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Title: The A B C of Mining
A Handbook for Prospectors
Author: Charles A. Bramble
Release Date: April 1, 2014 [EBook #45287]
Language: English
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THE A B C OF MINING
_A Handbook for Prospectors_
TREATING FULLY OF EXPLORATORY AND PREPARATORY WORK OF THE PHYSICAL
PROPERTIES OF ORES, FIELD GEOLOGY, THE OCCURRENCE AND ASSOCIATIONS OF
MINERALS, METHODS OF CHEMICAL ANALYSIS AND ASSAY, BLOW-PIPE TESTS,
PROMISING INDICATIONS, AND SIMPLE METHODS OF WORKING VALUABLE
DEPOSITS, TOGETHER WITH CHAPTERS ON QUARTZ AND HYDRAULIC MINING AND
ESPECIAL DETAILED INFORMATION ON PLACER MINING, WITH AN ADDENDA ON
CAMP LIFE AND MEDICAL HINTS.
BY
CHARLES A. BRAMBLE, D.L.S.,
Late of the Editorial Staff of "The Engineering and Mining Journal,"
and formerly a Crown Lands and Mineral Surveyor for the Dominion of
Canada.
_ILLUSTRATED._
CHICAGO AND NEW YORK:
RAND, McNALLY & COMPANY,
PUBLISHERS.
Copyright, 1898, by Rand, McNally & Co.
PREFACE.
Owing to recent rich discoveries in more than one mining field,
hundreds of shrewd, intelligent men without experience in prospecting
are turning their attention to that arduous pursuit--to such this book
is offered as a safe guide.
A complex subject has been treated as simply as its nature permitted,
and when a scientific term could not be avoided, the explanation in
the glossary has been offered.
CHARLES A. BRAMBLE, D.L.S.
PREFACE TO SECOND EDITION.
A steady demand for this work has shown that it fills a want, and
serves the purpose for which it was written. In issuing this second
edition, a few compositors' errors that had crept in, owing to the
author being in a very remote region while the book was going through
the press, have been corrected, but no material changes in the text
were found desirable.
CONTENTS.
THE A B C OF MINING.
PAGE
Chapter I--Prospecting, 7
II--How to Test for Minerals, 38
III--Blow-Pipe Tests, 65
IV--Economic Ores and Minerals, 75
V--Mining, 100
VI--Camp Life, 143
VII--Surveying, 155
VIII--Floating a Company, 161
IX--Medical Hints, 165
X--Dynamite, 168
XI--Atomic Weights, 170
XII--Odds and Ends, 172
Glossary, 181
A B C OF MINING.
CHAPTER I.
PROSPECTING.
Many men seem to think that should their destinies lead them into
parts of the world where there is mineral wealth they will have little
chance of discovering the deposits without the technical education of
a mining engineer. This is wrong. The fact is that the sphere of the
prospector does not cover that of the engineer. The work of the one
ends where that of the other begins, and many of the most successful
discoverers of metallic wealth have been entirely ignorant of the
methods by which a great mine should be opened, developed, and worked.
A few simple tools and a not very deep knowledge of assaying, with an
observant eye and a brain quick to deduce inferences from what that
eye has seen, are the most valuable assets of a prospector. In time he
will gain experience, and experience will teach him much that he could
not learn in any college nor from any book. Each mining district
differs from every other, and it has been found that certain rules
which hold good in one region, and guide the seeker after wealth to
the hidden treasure that has been stored up for eons of time, do not
apply in another region.
To show what may be done with imperfect, improvised apparatus, an
Australian assayer, who has since become famous, started up country in
his youth with the following meager outfit: A cheap pair of scales, a
piece of cheese cloth, a tin ring 1-1/2 inches by 1/2 inch, a small
brass door-knob, some powdered borax, some carbonate of soda and
argol, a few pounds of lead lining taken from a tea chest, an empty
jam pot, a short steel drill, a red flower pot. With this modest
collection of implements he made forty assays of gold ores that turned
out to be correct when repeated in a laboratory.
About the best advice that can be given to a man who has determined to
go to some out of the way region where there is a possibility of his
discovering minerals is to recommend him to visit the nearest museum
and gain an acquaintance with the common rocks. Should he be unable to
do this he had better provide himself with small, inexpensive
specimens from the shop of some dealer. It is almost impossible to
teach a beginner to distinguish the various rocks by any amount of
printed instruction; the only way to learn to recognize them is to
handle them and note carefully their color, weight, and the minerals
that go to make them up. The explorer should be able to recognize at a
glance, or at any rate after a very short inspection, the sedimentary
rocks, such as sandstone and limestone; the metamorphic rocks, that
is, rocks that have been altered by the agency of great subterranean
heat in ages long past, and which were probably stratified rocks at
one period, such as granite and gneiss, and the truly igneous
rocks--trap, diabase, diorite, etc. He must know also that mysterious
rock which the western miner calls porphyry, and to which is ascribed
most wonderful virtues in the way of ore attraction; while dolerite
and dolomite must be to him familiar terms and substances. This sounds
easy enough but the student will find that a good deal of hard work is
necessary before he can readily recognize each of these rocks.
It is even more necessary that he should learn the metals thoroughly.
Each one differs from all the rest in some particular. Often this
difference will be an obscure one, but to the careful investigator the
recognition of the substance will be in the end certain. They may
differ in weight, in color, in hardness, in a dozen different ways, so
that to the man who has made a study of this subject a determination
is always possible.
On account of the wonderful discoveries in the Canadian Northwest and
in Alaska, the eyes of thousands are turned towards those fields.
Wonderfully rich placer ground has already been found and there can be
no reason to doubt that very much larger areas remain unproved. Where
this gold comes from is an open question; geologists, mineralogists
and chemists, not to mention mining engineers and practical
prospectors, have disputed over the source of the gold already found,
but it must be confessed that there are almost as many theories as
there are disputants. Could it be known with certainty how and under
what conditions the gold got where it is found, the problem of seeking
for it might be made easier. Unfortunately this is not the case, and
all prospecting for the home of the precious metal is more or less a
groping in the dark. We do know that the heaviest particles of gold do
not travel far from where they were first deposited, because gold is
so enormously heavy--its specific gravity being about nineteen times
that of water--it seeks the bottom of the stream and stays there. It
is not an invariable rule that the gold increases in coarseness as the
stream is ascended, but it is a very general one. On some rivers rich
and poor stretches of gold-bearing gravel succeed one another as the
explorer makes his way up or down stream. This is difficult to account
for, but in many cases is believed to be caused by the modern river
robbing the bed of some one or more ancient water-courses whose beds
crossed the valley of the present stream. This may or may not be the
case. We only know that the miners who found coarse gold on the lower
regions of such rivers as the Frazer were miserably disappointed when
they reached stretches near the source and found nothing but flour
gold. This same feature has been noticed in some of the Alaskan
rivers. It is quite within the bounds of probability that no very rich
quartz veins exist in Alaska. It does not follow from the richness of
the placers that the gold is derived from very rich quartz lodes,
because this amount of gold may really represent the product of a vast
amount of rock that has been ground to powder and washed away in the
course of ages. The gold would not travel far, and the deposits being
unearthed to-day have been accumulating in these northern streams
since the world was young; water-courses are nature's ground sluices.
It is possible that one stream has cut through the drainage of
another. Sometimes this has impoverished the first and enriched the
second, while in other cases the reverse has obtained. Upheavals have
formed faults[1] and fractured the strata, and the gold may have been
deposited by solution in these fractures. Often the soil will have
been washed away from near the top of the mountain, so that layers of
stratified rock are seen to be duplicated on each side while they are
covered at the summit. The prospector keeps his eye open as he goes
along and notes carefully the character of the fragments of rock he
finds in the streams. Quartz, diorite, diabase, and porphyry pebbles
are grounds for expecting a profitable result, but of course there is
no certainty of such a happy issue. As soon as the district begins to
be fairly well known certain discoveries are made that invariably
render prospecting easier. Local peculiarities are noted; certain
characters are found to be common to the ore-bearing bodies or
deposits; the lines of deposits become known, and a good deal of light
is then shed upon a very difficult problem. As a rule, when the
fragments of quartz, pyrite, chalcopyrite, or galena are rough, they
have not traveled far, and the lode from which they have been derived
should be close at hand. Water and attrition soon round these minerals
on their sharp edges, and thus show that they have come from some
little distance.
[1] Dislocation of the strata.
In some countries, especially where vegetation is scanty, the outcrop
of a body of mineral may be traced by a difference in the vegetation.
In South Africa a chain of pools usually follows the course of a line
fault, which in its turn marks where an intrusive lode carrying
mineral separates two different formations. As a rule, any heavy
mineral is worth investigating. Even in remote regions silver,
mercury, tin, nickel, platinum, copper, and several other metals are
worth paying attention to. If they are too far away from the railroad
or the steamboat to-day they may not be so next year, for civilization
advances with giant stride in these days and never faster than when
transportation companies are reaching forth to some newly discovered
mineral field.
One of the greatest drawbacks to prospecting in the North is the dense
growths of moss and forest that cover the ground. In most of the
Western states, in South Africa, and in Australia this drawback does
not exist and prospecting was by that much the easier. However, as a
compensation, there is abundant water in Alaska and the Northwest,
while it was and is almost entirely absent in several other regions
that possess immense bodies of ore which are not available for this
very reason.
Quartz has been called the mother of gold, and certainly quartz and
gold are inseparably connected to-day. As to where gold may be found
the best reply that can be given is in the words of the old miner,
who, when asked that question, said: "Where it be's; there it be's,"
and then added, "and there ben't I."
Although most prospectors travel alone from sheer necessity, there can
be no doubt that three or four men forming a party and working
together have the advantage. They can do their work cheaper, more
thoroughly, and more surely. By co-operating they may carry a more
complete outfit. Should any accident happen help is at hand, whereas
the solitary wanderer often dies as the result of some accident that
would have been trivial had he had a companion. Three or four claims
may be worked in conjunction with one another at far less
proportionate expense than a single one could.
Nature's preparation for the reception of great ore deposits is
somewhat as follows: The crust of the earth is prepared for the
reception of the metals by great outbursts of igneous or melted rocks;
the metals themselves being carried in suspension in the heated water
that everywhere traverses the strata. These metals are deposited in
the veins as soon as the waters begin to cool, and the pressure to
which they were subjected from deep down in the earth's crust is
removed. A great mineral country is usually marked by the outcrops of
the veins being persistent in their courses and traceable for many
miles, though very probably many breaks may occur in these outcrops.
The rocks associated with great ore bodies are lime, porphyry,
granite, shales, slates, quartzites, and diabase. Fragments of mineral
and gangue, known to the miners as float, may be littered over the
hills and encumber the courses of the stream. A central line of
eruption may often be traced by masses of altered rock, and beds of
lava or other volcanic products. We find the granite has been melted
and the limestone has acquired magnesia, and thus become dolomatized.
Whenever a heavy deposit of pyrites, or mundic, is found mineral
probably exists below. The cubes of pyrite are not always valueless,
they may contain gold in addition to the iron and sulphur. When the
pyrites decay under the influence of the weather, and leave the quartz
honeycombed, these cavities often contain concentrated gold; for which
reason you often get a higher assay from the surface than from any
point lower down in the vein. In sinking the shaft soon gets below
this altered quartz and the ores are then combined with sulphur. They
have become sulphides, and are harder to treat. The prospector should
therefore act very cautiously when trying to develop a mine with a
small capital behind him; because, although the first ore may be
adapted for stamping, he may find, before he has gone down fifty feet,
that it can only be treated in a smelter, and that all the money he
has put into crushing apparatus is wasted.
Without the prospector there would be no mining and the world would
yet be in the stone age. He is not appreciated at anything like his
real worth. He requires ability and experience, push and perseverance.
Prospecting is a search for valuable minerals. He may not be very
deeply learned in either geology or mineralogy, but he must have a
keen eye and good natural powers of observation.
There are some sixty or seventy elements in the world, and the most
common is oxygen. Nearly all the coloring matter of rocks comes from
iron. Wind, frost, rain, snow, and heat, cause a crumbling of the
different rocks, and running water wears them away, and carries off
and distributes the particles. By this agency, and by floating ice,
they are often removed to long distances. The action of internal heat
renews the deposits of mineral by eruption, or by hot springs, but
this means of renewal was much more powerful in the past than it is
now.
Organic matter found in the crust of the earth was derived from
animals or vegetables. Coal is a legacy from forests that flourished
ages ago, while petroleum is all that remains of vast schools of
fishes that swarmed in Devonian seas.
Stratified rocks are either sand, clay, or calcareous, which means
lime-bearing. In their natural position they were horizontal, but
owing to subsequent volcanic action they are, in some localities,
tilted at all conceivable angles. The eruptive rocks have burst
through them in places, changed their character, divided them by
intrusive masses, and generally enriched them with mineral deposits.
Everything now known points to the theory that the contents of veins
were deposited in the lodes by infiltration. In a few instances famous
mines have no veins, but are literally hills of mineral; they are then
of low grade, but much more remunerative than average high grade
mines, owing the vast quantity of ore, and the ease with which it can
be mined. The famous Treadwell mine, on Douglas Island, Alaska, has
ore that is worth less than four dollars a ton, but it is quarried,
and 640 stamps work day and night. There is about a dollar a ton
profit, and hundreds of thousands of tons are treated annually. The
tin mine known as Mount Bischoff, in Tasmania, and the Burra copper
mine in Australia are other instances. Each of these deposits was
found as an outcropping on the bare top of a low hill, and none of
them has walls.
A fault may throw the vein up or down, and a good deal of exploration
may have to be done before it is recovered.
A lenticular vein consists of a series of double pointed ore bodies
like lenses which may be strung out, overlapping, or not.
The outcrop of a vein is never the same as its strike, except on a
level surface.
A stringer of ore branching off from the main vein is known as a
chute, shoot, or chimney.
In developing a ledge or lode, first find out what the ore is. Gold is
shown in the mortar, especially after roasting. Silver may be
recognized at sight, or by assay tests, or blow pipe; copper, by its
vivid colors,--green or blue for carbonate and red for oxide or
metallic copper. The ore often differs in various parts of the vein.
Explore your lode along the surface, across, and down its dip. When
you find it continuous it will be time enough to think of a vertical
shaft. The top of a shaft must be timbered with logs, so as to give
sufficient fall to get rid of the mineral when it is hoisted.
The first thing the prospector has to consider is his outfit. The more
complete this is the better, but ninety-nine times out of a hundred
the difficulties of transportation in a wild region are so enormous
that he will have to do without a great many things that he would like
to have. He must endeavor to make up for the lack of tools by
ingenuity; then he may get along fairly well. A pan, he must have. In
this he will wash carefully all his samples. Then, a flask of
quicksilver is more precious to him even than gold; for, having it, he
can resort to pan-amalgamation, which will save the precious metal
even when it is in minute particles.
This process may be described as follows: A pound or two of the ore in
powder is placed in the pan and water is added until the mass becomes
a thin pulp. One ounce of quicksilver and a small piece of that deadly
poison, known to the chemist as cyanide of potash, and as prussic acid
to the ordinary man, should be added, and the mass should be stirred
thoroughly, for two hours if you can stand it. Then turn in water and
wash off the dirt and the amalgam will be found in the bottom of the
pan. This you must collect very carefully. You should have a square
piece of chamois skin or a piece of strong white cotton cloth. In
either case the amalgam is put in the center of this square and the
cloth twisted until all the superfluous quicksilver is pressed out and
your amalgam remains nearly free from mercury. This amalgam placed on
a shovel and held over a brisk fire will soon show the yellow color of
gold. If you have no mould you may make one of clay, put your gold
therein with a little borax, and very soon, the fire being hot enough,
you will have a tiny ingot of the precious metal. But most prospectors
are satisfied when they have obtained their sponge gold, and do not
carry their operations further in these rough and ready tests.
The prospector of to-day is often a very different man from his
predecessor of a generation ago. The old gold hunter used to sally
forth armed with a pick, shovel and pan, and usually a very little
grub. In his stead men are now taking the field who have had the
benefits of a thorough education, both practical and theoretical, and
provided with all the equipment necessary for their work. Some of
these men carry an outfit somewhat as follows: An iron mortar holding
half a gallon, together with a pestle a rough scale for pulp, a more
delicate one showing troy grains and pennyweights, a 40-mesh sieve, a
burro furnace and muffle, one cupel mould, a couple of dozen
scorifiers, tongs to handle the cupel and scorifiers, two annealing
cups, a spirit lamp, a dozen test tubes, a pouring mould, five or six
pounds of borax and about as much carbonate of soda, five pounds of
bone ash, ditto of granulated lead, a pint of nitric acid, ditto of
hydrochloric acid, ditto sulphuric acid, ditto of ammonia, twice as
much alcohol and two pounds or so of granulated zinc.
As a blow pipe outfit he will take a blow pipe, spirit lamp, nitrate
of cobalt in solution, cyanide of potash, yellow prussiate of potash,
red prussiate of potash, a sheet or two of filtering paper and a
couple of three-inch glass filters. With this outfit he can determine
any mineral he may come across.
By patience and observation the man who starts out to take up
prospecting as a road to fortune may easily master the rudiments of
his business. It will not take him long to become familiar with the
commoner rocks, and the more valuable ores. His own rough tests in the
field must be confirmed by competent assayers upon his return to
civilization, and in this matter he should be very guarded. The most
reliable assays are made either at the different government assay
offices or by some of the large metallurgical works whose reputation
is world wide. Prospecting is hard work, but the life is healthy and
full of excitement, only the explorer should have courage, hope, and
good temper, for each and every one will be as necessary in his chosen
vocation as his pan and pick.
When alluvial or placer gold has been found it is reasonable to
suppose that the vein from which it was derived may also reward
diligent search, for it is undoubtedly true that most placer gold has
come from quartz veins. This, however, is believed not to be
invariably the case, a recent school of mineralogists contending that
pure masses of alluvial gold have been formed from the accretion or
growth of the gold deposited from certain gold salts. This is in any
case probably exceptional, and the prospector who finds gold in gravel
should seek in the adjacent country for the quartz lodes from which it
came.
Important deposits may be expected at or about the line of
unconformability where slates, shales, quartzites, sandstones,
limestones, schists and other sedimentary deposits are pierced by
intrusive masses of igneous rocks.
Veins filling the cracks that once existed between two differing rocks
are known as contact veins. Such veins are often very rich. Curiously
enough large masses of true igneous rock rarely contain valuable
deposits of mineral, but where such intrusive masses cut dikes or
walls of porphyry, or diorite, the region is worthy of careful
investigation.
[Illustration: POCKET LENS.]
In an open country the prospector should keep to the hill tops if on
the lookout for veins, as the outcrops show more distinctly on the
bare ridges, but alluvial deposits are only found in valleys and along
the borders of streams. In any case, much of the northern part of this
continent can only be prospected by following the streams, on account
of the dense growth of forest with which the soil is covered. The true
line of strike of a vein can be determined only on a level stretch.
The line of strike and the line of dip are always at right angles to
one another; the outcrop may follow the strike or it may not.
A pick, shovel, and pan, are absolutely necessary to a prospector's
proper equipment. A good pocket lens, cheesecloth screen, and small
iron pestle and mortar are often useful. The pan is the most essential
part of the outfit, and is always bright from use.
The regular gold miner's pan is 13-3/4 inches in diameter across the
top, 10 inches across the bottom and 2-1/8 inches deep. The best are
made of sheet iron and have a joint around the bottom rim which is of
some assistance in retaining the spangles of gold.
A more primitive instrument than the pan is the batea. This requires
more skill than the pan, and is much in favor with South American
miners. It is made of hard wood, 20 inches in diameter, 2-1/2 inches
deep in the center, inside measurement, and sloping gradually to
nothing at the sides.
The horn spoon has been handed on from antiquity. It is made from a
black ox horn, at least a black one is the best as it shows the gold
better; it is eight to ten inches long by three inches wide, cut off
obliquely.
When gold is suspected in quartz, but there is visible to the naked
eye more or less iron, copper, and other base metals, it is well to
crush the quartz into coarse fragments. Roast on a shovel or other
convenient tool over a hot fire, and finally pulverize in the mortar.
If panned it will now reveal much of its gold, while, had these
measures not been taken, the sample might have given negative results
and been declared valueless.
After pulverizing, the ore should be passed through the cheese cloth
screen before panning. If the approximate value of the ore is sought,
the sample must be dried and weighed before crushing; and the
resulting gold weighed. Thus:
Sample is to 2,000 lbs. as gold found is to Ans.
About 13 cubic feet of quartz weigh a ton before being disturbed; when
broken to medium sized lumps 20 cubic feet may be taken as
representing a ton. Although experience teaches the miner to estimate
very closely the value of his sample, it is better for the tyro to
have a small pair of scales with grain weights. A grain of gold, if
tolerably pure, is equal to four cents. Above all things avoid the too
common error of panning the pick of the rock, as a false estimate is
bound to follow and only too probably eventual loss.
A yard of gravel before being dug makes one and a half yards
afterwards. A pan of dirt is usually about 20 pounds, although it is
not well to fill quite full in actual work.
Many a valuable mine has been found by following up "float" ore. Float
is detached fragments of the vein or gangue, and it becomes more and
more abundant as the lode is approached until it finally ceases
abruptly. This indicates that the vein has been reached or passed, and
a trench dug throughout the alluvial soil at right angles to the
assumed line of the vein will probably reveal it. The float and
mineral of course drift down hill; if the side of the mountain be
saddle-shaped the float will spread out like a fan as it washes down,
but if concave the force of gravity will concentrate it within a
narrow space in the ravine. Float found at the foot of a hill has
come, as a rule, from that hill. The nearer the vein the less worn
will be the edges of the float and mineral. The gangue or vein-rock in
which the metal is found may be calcite or calc spar, fluor spar,
heavy spar or baryta, or quartz. Gold is almost always found in this
last matrix. The upper parts of most quartz lodes are usually
oxidized, that is to say, the atmosphere has acted upon the iron
pyrites, freeing the sulphur and staining the quartz yellow, red, or
brown, by oxide of iron. This is known as "gossan" or the "iron hat."
Such quartz is frequently honeycombed and rotten. Below the water
level these veins run to sulphides in which decomposition has not set
in, and the gold contained in the quartz is no longer "free milling,"
i.e. will not give up its gold to mercury without a preliminary
treatment.
Whenever the explorer comes across a mass of gossan he should sink a
trial shaft to the vein, as it is almost certain that below the
oxidized sulphides a body of mineral exists likely to encourage mining
operations.
Native gold is malleable, will flatten out under the hammer, and a
steel knife will cut it with ease. It almost invariably contains
silver, sometimes to the extent of one-fifth. A little practice will
enable the prospector to recognize it, for there is but one king
metal. Much gold is derived from copper and iron pyrites, and silver
and lead ores are a very large source of supply.
Gold is found in gravel of every variety, from finest pipe-clay to
boulders weighing tons. Sometimes volcanic eruptions have covered
these deposits since the ancient rivers laid them down, and in many
cases their courses do not in the least agree with the valleys of the
shrunken streams that have replaced them.
Gold may be distributed through the whole thickness of a bed, but
ninety-nine times out of a hundred the richest layer of gravel is just
above the bed rock upon which all the gravel rests. Gold may even be
found among the grass roots, especially in dry localities where there
has been little water to carry it downward. When the bed rock consists
of upturned slates the gold frequently penetrates it for some little
distance.
Sand is nearly always poorer than gravel.
The experience of miners in the Victoria gold fields is that gold is
always found on the bars or points, and not in the deep pools and
bends.
The great difficulty with which any but the very finest particles of
gold can be moved by water accounts for the value of the deposits
depending largely upon the local rocks. It is very fortunate that
gold's specific gravity is so great, for were it less its recovery
would be much more difficult. The sluices and other apparatus of the
miner are really nothing but the operations of nature imitated on a
much smaller scale. There is one thing, however, time, that nature can
afford to expend in prodigious periods, while man must not waste a
single minute.
It not being possible to point out where the ancient river beds lie,
smothered as they are by hundreds of feet of overlying drift, lava,
and other later deposits, the only feasible plan is a series of boring
with the diamond drill.
When gold has been discovered the finder must act with the greatest
prudence, for even gold may be bought too dear. The surest test is a
mill run, that is passing 10 to 50 tons through all the operations of
crushing, milling, roasting, amalgamating, etc., and so ascertaining
what returns are likely to be obtainable when the deposit is worked on
a commercial scale. True sampling is necessary. All parts of the vein
should be included, and the lode cross-cut by galleries in more than
one spot. It is the very great necessity of these expensive
preparatory explorations that has given rise to the saying, "Quartz
mining is for rich men."
Many gold mines have been abandoned as unprofitable that could have
been mined at a profit had their owners been wealthy and enterprising
enough to do a great deal of expensive prospecting by diamond drill,
cross cuts, drifts and rises. In one instance that came to the
writer's knowledge a clever mining engineer cleared nearly $200,000
profit by leasing for a term of years a gold mine that was supposed to
be exhausted. A drill hole sunk less than 50 feet below the old
workings revealed a pocket of ore in the vein, and paying quartz was
found for many hundred feet below.
With the improvements in electricity made recently a cheap power has
been provided that will permit many mines to be reopened. The saving
in working expenses effected by introducing electricity is often very
large; after the plant is once installed the cost is almost nil where
turbines can be employed to furnish the power to the generators.
Machinery capable of delivering power at a distance of several miles
from the plant, may be operated at very reasonable cost as compared to
that of other prime movers.
Discoveries of many deposits that have in time been successfully mined
were the result of chance. No skill guided the finder; he merely
stumbled upon his luck just as the wayfarer once in a while hits his
toe against a well-filled pocketbook. For instance, a South Australian
squatter picked up a piece of copper ore that a wombat had thrown out
of his burrow, and the result was the discovery of the great Wallaroo
lode. The first diamond from South Africa was picked up by an ignorant
bush boy and kept with a lot of worthless pebbles in the private
collection of the boy's master; no suspicion existed of its value
until a passing trader had carried it away and obtained $2,500 for it
in Capetown. Gold was first discovered in California in 1848 by the
superintendent of a sawmill who saw it glistening in the flume.
Similarly gold was discovered in both Australia and Brazil by the
purest chance. Had not a tree been uprooted by the wind the vast
deposits of soft hematite iron ore in the Biwabic iron mines of the
Mesabi range, Minnesota, might have remained unknown for many a long
year to come. In the desolate region to the northward of Lake Huron
great stores of nickel ore exist. These mines, which may some day
regulate the price of the metal all the world over, were exposed in a
railway cutting; no one dreamed of their existence. The Redington
quicksilver mine in California was discovered by some roadmakers.
Tradition relates that the enormously rich silver mines of Potosi, in
Bolivia, were discovered by the accidental uprooting of a bush having
spangles of silver ore attached to its roots. This was in 1538, and
two hundred years later a similar streak of luck revealed the wealth
of the Catorce district of Mexico, from which in thirty years, ore to
the value of $35,000,000 was taken.
Moreover, the search for one mineral often leads to the discovery of
another. The Comstock lode was first worked for gold, and the miners
threw away the black sulphide of silver worth $3,000 to the ton. The
Broken Hill mine in Australia was claimed as a tin deposit by its
finder; it is now the greatest silver producer in Australasia. Such
instances could be multiplied almost indefinitely, chance entering
into a majority of mineral discoveries. On the other hand, it has
happened, not infrequently, that purely scientific deductions and
calculations have brought to light stores of mineral wealth.
Certain minerals are likely to be found associated. Cassiterite goes
with boron and tourmaline, topaz, fluor spar and lithia-mica; all
containing fluorine. It is also found with wolfram, chlorite and
arsenical pyrites. Magnetite is often accompanied by rocks containing
garnet, epidote and hornblende. Zinc blend and galena may occupy the
same vein, which is likely to be of baryta or heavy spar. Much galena
carries silver. Gold is associated with many metallic sulphides such
as iron, magnetic, and copper pyrites, mispickel, galena, blend,
stibnite and tetrahedrite. Gypsum accompanies salt.
Surface indications may be described as: Form of ground, color,
outcrop, decomposed and detached mineral, mineral deposits from
springs, altered or peculiar vegetation and other similar guides. A
hard quartz outcrop often stands up like a wall and is traceable for
miles. The Rainbow silver bearing lode of Butte, Montana, stood 20
feet above the surface. Soft minerals, such as clay, are cut into and
sunk below the surrounding level. Deposits of Kaolin or China clay are
usually so found.
Any special bright coloration of the rocks of a district merits
investigation. Copper gives green, blue, and red stains; iron, red or
brown; manganese, black; lead, green, yellow or white; cobalt, pink;
cinnabar or quicksilver, vermilion. The nickel deposits of New
Caledonia were made known to the world by the explorer Garnier in
1863, his curiosity having been aroused by the delicate green coating
given the rocks by an ore containing water, quartz, nickel and
magnesium.
Hard beds of shale decompose on the surface into soft clay, and a
still more noticeable change is the conversion of ores containing
sulphur into oxides. This chemical change causes the gossan or "iron
hat," for which token of underlying wealth the prospector should be
eternally watchful. This alteration may extend downward four or five
hundred feet from the surface, but in such cases the true weathering
has ceased long before the limit of discoloration is reached, and the
change of substance is due to the filtering of surface waters through
the vein.
Gossan varies greatly in its nature. Galena becomes anglesite,
cerussite, pyromorphite and mimetite. Copper pyrite changes into
native copper, melaconite, cuprite, malachite, chessylite, or perhaps
into a phosphate, arsenate, or silicate of the metal. Carbonate of
manganese gives the black oxides and silver sulphide ores are, after
weathering, known as native silver, kerargyrite and embolite.
The ore in the gossan is very generally more valuable than it will be
below, and this is especially true of gold and silver ores. The gold
having been set free from the close embrace in which the iron pyrite
held it previous to the latter's oxidation, it is now readily caught
by quicksilver. Silver under similar conditions becomes chloride, and
likewise amalgamates without difficulty.
Seams containing native sulphur often show no trace of that element on
the surface, having weathered into a soft, white, gray or
yellowish-white granular, or pulverulent, variety of gypsum.
Veins of asbestos often decompose into a white powder found in the
crevices of the rocks; fibrous asbestos existing in the interior.
Petroleum shows in an iridescent film upon still pools, and the odor
is a sure guide to its nature.
A "dipping-needle" is valuable to the prospector on the lookout for
iron ore; by its use he may discover masses of magnetic ore and trace
their extent. As he carries the compass over the ground the needle
dips toward any iron mass he approaches; directly over the ore it
becomes vertical.
[Illustration: MINER'S DIPPING NEEDLE.]
In a wilderness country strength of body and endurance are important
qualifications. The prospector must, moreover, have such general
knowledge of geology and mineralogy as to be able to recognize all
valuable minerals and confirm his conjecture by simple tests. Pick,
shovel and pan must be handled skillfully, while the rifle, shotgun
and paddle must also be understood. For in the unsettled parts of the
country the traveler must even yet rely to some extent upon the fish
and game he may be able to secure, and every old prospector becomes a
trained hunter and camper. Knowing how to bake bread is sometimes more
valuable than much mathematics; ability to build a rough boat is often
the one hope of salvation.
In sinking a short shaft in a sunny country a large mirror, inclined
at a suitable angle over the shaft, will give sufficient light.
Lodes or veins following the general trend of the auriferous quartz
are much more likely to be rich than are those that cross it. Gold is
never distributed evenly in veins, though it may be in great beds of
low grade material; but more often rich areas alternate with barren
portions.
Where quartz veins are small and the rich pockets separated by wide
intervals of poor gangue the gravel of the district will usually be
similar in character. As this condition obtains in the upper Yukon
district as far as the gravels are concerned, it will probably be
found to hold good for the quartz leads, when they shall have been
discovered.
The more nearly the gold formation approaches to the crystalline
schists, the poorer will the quality of the gold be through the larger
percentage of silver found in it. In slates the proportion may be 22
gold to 1 silver; in schists it has been known to be a ratio of 1 to
1.
With the discovery of valuable gold-bearing gravel on the bare
hillsides of the Northwest, a vast region has been added to the area
the prospector may explore to advantage. No experience acquired in
ordinary American placer grounds is likely to be of much use in
detecting these higher gold-bearing gravels of the Yukon, but they
appear to be somewhat similar in character to the New Zealand
terraces. Terrace-prospecting requires perseverance and the use of
some brains, as it is infinitely harder than creek-prospecting. These
terraces or benches are the remains of old river beds. The whole bench
must be carefully scanned over because the gold is quite as likely to
be in one part as in the other. Sometimes it is in half a dozen
different layers one above the other. Sometimes the old river terraces
are entirely covered by landslides, and the majority of such deposits
are not likely ever to be found, as it is almost impossible to guess
at locations.
In New Zealand gold has been found on table-lands nearly 6,000 feet
above sea level, and according to recent information valuable claims
have been discovered in Alaska on the very summits of the rounded
hills on each side of El Dorado creek.
To understand how such deposits as those of the Northwest may have
been made, suppose that such a vein as that of the Idaho, which has
been worked for a depth 1,700 feet by a width of 1,000 feet, and from
which $17,000,000 have been taken, to have been worn down by glacial
or other forces. Is it not conceivable that the gold would gradually
have accumulated in the nearest canyon?
[Illustration: DOLLY.]
To obtain suitable samples of the vein a dolly is an efficient
apparatus.
This is practically a very simple, crude, stamp mill. On the end of a
solid log, firmly fixed in the ground and standing four feet or so
above the surface, a square 6-inch hole is cut in which are fitted
wrought iron bars 3 inches deep by 1/2 inch wide, and separated by
equal intervals. These bars taper below so as to permit free passage
of the pounded mineral. A wooden box surrounding the grating keeps the
ore in place. A block of wood, shod with iron, forms the stamper. The
miner hauls on the handles at every blow. The gold is saved on the
lower table.
No one of experience in mining would look for brown hematite in a
granite range, nor for black band, though such might be a likely
region for red hematite or magnatite.
The explorer should be familiar in theory at least with the locality
where he may expect to find valuable minerals. For instance, should he
be searching for some heavy, detached substance that is usually found
in placer deposits he will keep to the low ground and examine
carefully the beds of the streams. On the other hand, should his quest
be for some ore that is more properly a component of a lode or vein he
will examine the side hills and summits where denudation will
certainly have exposed such deposits. Then he must know the appearance
of each ore, and with the methods of making rough and ready tests he
must be perfectly familiar.
Gold is always more or less intimately associated with quartz. Oxide
of tin is said never to have been found more than two miles from some
granite rock, one of the components of which was muscovite or white
mica. The junction of slates and schists with igneous or metamorphic
rocks often proves a valuable find of mineral.
Rocks for the purposes of the explorer may be grouped under three
heads: Igneous; metamorphic; stratified. The first includes lavas;
trachytes, grayish with rough fracture and mainly glassy; dark
basalts: and traps, such as greenstone. Obsidian is a volcanic glass.
Metamorphic rocks are thought to have once been stratified, but to
have been altered by heat. They comprise granite, of quartz feldspar
and mica; syenite, containing hornblende instead of mica; gneiss, like
granite, but showing lines of stratification; mica schist, made up of
mica and quartz and separating easily into layers; slates.
Stratified rocks are those deposits from water, such as sandstone,
limestone, clay, etc.
A prospecting shaft need not be of large dimensions. One 4 feet square
is amply large for any depth down to 30 feet, but it must be kept
plumb.
Sometimes shafts are sunk through the pay streak in alluvial gravel,
without it being detected. Frequent panning will guard against this
mistake.
In the Klondike region it is said early prospectors missed very rich
deposits, that have since been discovered, by stopping short of true
bed rock, being misled by a bed of harder gravel that they thought was
bottom.
Silver almost invariably carries some gold. The dark ironstone hat
already referred to is a good indication of silver ore beneath; it is
generally composed of conglomerates cemented by oxides of iron and
manganese.
Galena, which is sometimes so rich in silver as to be worth working
for that metal, may often be followed by surface indications; namely,
a white limy track with detached fragments of float ore in the surface
soil. The blowpipe or fire assay quickly determines silver ore.
Tin in lode, stream, or alluvial deposits occurs only as an oxide, but
its appearance is varied. It may be almost any color and shape. It is
always near granite, containing white mica known as muscovite.
The minerals for which it is most easily mistaken are:
Sp. gravity. Streak.
Wolfram 7 to 7-1/2 Red, brown or black.
Rutile 4.2 Light brown.
Tourmaline 3.2 Whitish.
Black Jack 4.3 Yellow, white.
The magnetic or dipping needle is used in New Jersey, as follows,
according to the State Geologist, W. H. Scranton, M.E.: "An
attraction which is confined to a very small spot and is lost in
passing a few feet from it, is most likely to be caused by a boulder
of ore or particles of magnetite with rock. An attraction which
continues on steadily in the direction of the strike of the rock for a
distance of many feet or rods, indicates a vein of ore; and if it is
positive and strongest towards the southwest, it is reasonable to
conclude that the vein begins with the attraction there. If the
attraction diminishes in going northwest, and finally dies out without
becoming negative, it indicates that the vein has continued on without
break or ending until too far off to move the compass needle. If, in
passing towards the northwest, along the line of attraction, the south
pole is drawn down, it indicates the end of the vein or an offset.
If, on continuing further, still in the same direction, positive
attraction is found, it shows that the vein is not ended, but if no
attraction is shown, there is no indication as to the continuance of
the ore.
"In crossing veins of ore from southwest to northwest, when the dip of
the rock and ore is as usual to the southeast, positive attraction is
first observed to come on gradually, and the northwest edge of the
vein is indicated by the needle suddenly showing negative attraction
just at the point of passing off it. This change of attraction will
be less marked as the depth of the vein is greater, or as the strike
is nearer north and south. The steadiness and continuance of the
attraction is a much better indication of ore than the strength or
amount of the attraction. The ore may vary in its susceptibility to
the magnetic influence from impurities in its substance; it does vary
according to the position in which it lies, that is according to its
dip and strike; and it also varies very much according to its distance
beneath the surface."
Further instructions are given in the paper from which the foregoing
extract was taken, some of which follow:
"It is sufficient to say that the first examinations are made by
passing over the ground with the compass in a northwest and southwest
direction, at intervals of a few rods, until indications of ore are
found. Then the ground should be examined more carefully by crossing
the line of attraction at intervals of a few feet, and marking the
points upon which observations have been made, and recording the
amount of attraction. Observations with the ordinary compass should be
made, and the variation of the horizontal needle be noted. In this way
materials may soon be accumulated for staking out the line of
attraction, or for constructing a map for study or reference.
"After sufficient exploration with the magnetic needle, it still
remains to prove the value of the vein by uncovering the ore,
examining its quality, measuring the size of the vein, and estimating
the cost of mining and marketing it. Uncovering should first be done
in trenches dug across the line of attraction, and carried quite down
to the rock. When the ore is in this way proved to be of value regular
mining may begin. In places where there are offsets in the ore, or
where it has been subject to bends, folds, or other irregularities, so
that the miner is at fault in what direction to proceed, explorations
may be made with the diamond drill."
CHAPTER II.
HOW TO TEST FOR MINERALS.
When the mineralogist wishes to know the names of the specimen he
holds in his hand, he, in the case of a mineral difficult to
determine, considers all the following properties:
Crystalline form and structure,
Cleavage,
Fracture,
Tenacity,
Hardness,
Specific Gravity as compared with that of water,
Luster,
Color and Streak,
Transparency or otherwise,
Taste,
Odor,
Chemical Composition tested by analysis,
Pyrognostic characters as determined by the use of the blowpipe,
Mode of occurrence and associated minerals.
Crystalline Form and Structure. Unfortunately the science of
crystallography is extremely complicated and long study is
necessary to master it; once acquired, however, it is of
paramount usefulness to the student. According to Dana there are
six systems, to one of which every crystal may be referred. They
are:
(1) Isometric; (2) Tetragonal; (3) Hexagonal or
Rhombohedral; (4) Orthorhombic; (5) Monoclinic; (6)
Triclinic.
In the isometric system there are three equal axes at right angles to
each other.
In the tetragonal system there are three axes at right angles to each
other. Two of these are equal, while the third, or vertical angle, is
longer or shorter.
There are two divisions of the hexagonal system; the hexagonal system
properly so-called, and its rhombohedral division. All forms are
referred to four axes, three equal axes inclined to each other at
angles 60 degrees in a common horizontal plane, and a fourth vertical
axis at right angles, and longer or shorter. The rhombohedral division
comprises crystals having but three planes of symmetry, intersecting
at angles of 120 degrees in the vertical axis. They are regarded as
half forms of the corresponding hexagonal crystals.
In the orthorhombic system there are three unequal axes at right
angles to each other.
In the monoclinic system there are three unequal axes, of which one,
the lateral axis, is inclined to the vertical, while the angles
between the others are right angles.
In the triclinic system there are three unequal axes and these
intersections are all oblique. The student who wishes to pursue this
subject further should consult Dana's System of Mineralogy.
Physical Mineralogy. Cleavage is the line of easiest separation in a
mineral. It may be perfect, imperfect, interrupted, etc.
Fracture, referring to any surface except that of a cleavage fall, may
be uneven, conchoidal (shell-like), hackly (rough), etc.
Tenacity refers to such qualities as brittle, sectile, malleable,
flexible, or elastic.
Hardness is represented by the difficulty with which a smooth surface
is scratched. The scale in general ore was devised by Mohs. It is:
1. Talc. Scratched by the finger nail.
2. Gypsum. Ditto, but with more difficulty. Will not scratch a copper
coin.
3. Calcite. Scratched by a copper coin.
4. Fluorite. Is not scratched by a copper coin and does not scratch
glass.
5. Apatite. Scratches glass, but with difficulty. Is readily scratched
by a knife.
6. Feldspar. Scratches glass with ease. Is difficult to scratch by
knife.
7. Quartz. Cannot be scratched by a knife and readily scratches glass.
8. Topaz. Harder.
9. Corundum. Harder.
10. Diamond. Scratches any other substance.
Hardness may be intermediate. For instance, any mineral that scratched
quartz and is soft enough to be scratched by topaz, in turn would be
rated at 7.5.
Specific Gravity. This is the density of mineral and other substances
compared with that of water. It is particularly valuable in
determining heavy metals.
To find the specific gravity of any solid body divide its weight in
air by the loss of weight in water, at a temperature as near 60
degrees F. as possible, and the quotient will equal the specific
gravity. In the case of gases, such as nitrogen, oxygen, etc.,
hydrogen is taken as the unit.
Luster. There are seven kinds of luster, viz: Metallic, the luster of
metals; adamantine, that of the diamond; vitreous, of broken glass;
resinous, of the yellow resins; greasy; pearly; silky. There are five
degrees of intensity of luster recognized, viz: Splendent; shining;
glistening; glimmering; dull.
Color and Streak. The streak is the color of the powder of the mineral
when rubbed on unglazed porcelain, or scratched with a knife.
Transparency. Minerals may be transparent, sub-transparent,
translucent, sub-translucent, opaque.
Taste. Minerals may be salt, bitter, sweet, etc.
Odor. This test is not of much use with most minerals until heat is
applied. All the petroleum oils, however, are often detected by their
odor.
Chemical Composition. This may always be determined by suitable tests
with reagents.
Pyrognostic Characters. As a means of readily determining the nature
of a specimen the blowpipe is unrivalled--if in the hands of one who
understands it.
Mode of occurrence and associated minerals. A knowledge of these
matters often assists in a determination.
A regular fire assay is not within reach of many prospectors, for the
necessary apparatus cannot, as a rule, be carried in the wilderness.
Whenever possible, however, a fire assay gives the truest results,
especially in the case of gold and silver.
[Illustration: SCALE FOR WEIGHING ORE.]
The operation includes testing the ore, sampling and pulverizing,
weighing the ore and reagents, calcination and roasting, reduction and
fusion, distillation and sublimation, scorification and cupellation,
inquartation and parting the gold and silver, weighing and tabulating.
"Notes on Assaying" by Dr. Ricketts is a very useful manual to have at
hand.
A TOLERABLY COMPLETE OUTFIT INCLUDES:
A pair of scales for weighing ore and buttons of base metal. It should
take 10 ounces in each pan, and show 1/20 of a grain.
A bullion scale to be kept strictly for the precious metals. Loaded
with one gramme, it should show 1/20 of a milligramme.
[Illustration: ASSAY BALANCE FOR BULLION.]
Weights. Avoirdupois; troy, metric and "assay." Assay weights save
much calculation. The unit of the system is a weight of 29.166
grammes. Its derivation is as follows:
2000 lbs. : 1 A.T. :: 1 oz. Troy : 1 milligramme.
To use this system, weigh out one A.T. of the ore and whatever number
of milligrammes of gold and silver the assay gives indicates an equal
number of Troy ounces to the ton of 2000 lbs. Avoirdupois.
A muffle and a melting furnace, portable and of medium size, are
handy, though furnaces may be built of ordinary brick, lined with fire
brick, that would be better for permanent use.
The fuels may be coke, anthracite or bituminous coal, charcoal, oil or
gas.
[Illustration: ASSAY FURNACE.]
[Illustration: PORTABLE ASSAY FURNACE.]
Crucibles of black lead, French clay, Hessian sand, and quicklime are
necessary to hold the assay.
[Illustration: French Clay. Hessian.
CRUCIBLES.]
[Illustration: SCORIFIER]
[Illustration: STEEL CUPEL MOULD.]
Roasting dishes, scorifiers and cupels are required. The cupel is made
of the ashes of burnt bone, and it is better to make them on the spot,
as the bone ash may be carried anywhere without damage, whereas the
cupels are very fragile. The bone ash is moistened with water, stamped
in a cupel mould, and allowed to dry slowly. A good one will absorb
its own weight of lead, but it is better to calculate on its absorbing
but three-quarters of that amount.
[Illustration: SCORIFICATION FURNACE.]
[Illustration: SCORIFICATION MOULD.]
The crucible, scorification and cupel tongs, a couple of hammers, iron
pestle and mortar, sieves from 20 to 100 mesh, and scorification mould
complete the requisite tools.
[Illustration: HAMMER.]
[Illustration: HORN SPOON.]
[Illustration: STEEL MORTAR.]
[Illustration: ALCOHOL LAMP.]
In addition, however, the assayer will require quite a bulky lot of
apparatus, reagents and chemicals. All dealers keep lists of assayers'
supplies on hand, and a full and complete assortment will cost about
$200 in New York or Chicago. Quart bottles, with glass stoppers;
ordinary corked bottles, ring stands, alcohol lamps, wash bottles,
test tubes, horn spoons, iron pans, parting flasks, annealing cups,
glazed black paper--these will suffice, provided the assayer has, as
well, the outfit recommended for blow-pipe work.
[Illustration: TEST TUBE.]
Dry reagents, such as litharge, borax (crystallized), silica, cyanide
of potassium, yellow prussiate of potash, argol, charcoal, starch,
metallic iron, pure lead, nitre, powdered lime, sulphur, carbonate of
ammonia and common salt are necessary. As solvents and precipitants,
distilled water, sulphuric, nitric and hydrochloric acids, chloride of
sodium, nitrate of silver and sulphuretted hydrogen are also
indispensable.
This will seem rather a formidable list, and so, under certain
conditions, it may be; indeed, where means of transport is limited,
all regular assay work must be postponed until the return to
civilization. Assaying is not, however, difficult, being mostly a
matter of rule of thumb, and correct results may be arrived at without
a deep knowledge of chemistry, although such knowledge will never come
amiss.
A preliminary examination will show what the ore probably is. The
blow-pipe is especially useful, though to the skilled assayer often
unnecessary. The ore is first powdered, and any metallic flakes picked
out and tested separately. A fair sample must be selected, otherwise
all the work will be thrown away and the result be valueless.
The next step is weighing the ore and the reagents. Moisture is drawn
off by heating in a crucible, a low heat being sufficient. Roasting
will eliminate sulphur, antimony, arsenic, etc., and must take place
in a flat dish, so that the air may have free access. The powder
should be stirred frequently.
Reduction is the operation of removing oxygen, and it takes place
usually in a crucible or scorifier.
Scorification consists in placing the ore in an open dish with proper
reagents, and collecting all the volatile ingredients in the slag.
Cupellation, on the other hand, collects them in the bone ash, of
which the cupel is composed.
When silver must be separated from gold, it is sometimes convenient to
increase its proportion by the addition of some known weight of the
inferior metal. After fusing, the globule is placed in nitric acid,
and the silver parted from the gold, which may then be weighed. This
result subtracted from the weight of the original globule gives the
amount of silver.
To test an ore for gold, take a pound of it, crush in mortar and pass
through a fine sieve. Take one-fourth ounce Troy of the powder. Place
in scorifier with an equal amount of litharge. Cover with borax that
has been melted and powdered, and put the scorifier in the muffle of
the furnace. A blacksmith's forge might do at a pinch. Heat until the
mass has become a fluid, possibly twenty or thirty minutes. Next pour
into the scorification mould, and, after the slag has set, remove it
with a hammer. Hammer the button into a cube and place it in the
cupel, which must first have been thoroughly heated. Heat until all
the base metal has been absorbed by the cupel and the button has
"brightened," or flashed; when this occurs, remove the cupel to the
front of the muffle, cool, and remove the button with pincers. Weigh
it, and you have the amount of gold and silver in 1/4-ounce Troy. A
simple sum in proportion gives the amount in a ton.
All ores containing sulphur, arsenic, antimony, or zinc, should be
roasted.
There are three stages in the scorification process; roasting, fusion,
and scorification. During the first, the heat should be moderate until
fumes cease to be given off; during the second, the heat is raised and
a play of colors is seen on the surface of the lead; in the closing
stage, the heat is lowered for a time until the slag covers the lead,
when it is again raised for a short time and the scorifier removed.
Brittle buttons may be due to arsenic, antimony, zinc or litharge, and
must be re-scorified before cupellation, with more lead.
Take the cupel slowly from the fire to avoid "spitting," by which
portions of the buttons are lost. Watch closely for the brightening.
Silver is volatile at a high heat, but when the muffle is almost
white, the metal well fused and clean, the fumes rising slowly, and
the cupel a cherry red, all is going smoothly. If the fumes rise
rapidly, the muffle is too hot. On the other hand, dense, falling
fumes show the temperature is too low. Lead that is poor in silver
stands the highest heat without vitiating the assay.
When the material in the cupel "freezes," i.e., the absorption by the
cupel stops, reject the assay and try again, giving more heat or more
lead.
Gold. Practically, the metal most prospectors seek is gold. It is so
enormously valuable and constitutes so very small a percentage of any
ore, that care must be taken or it may escape detection and be lost.
Panning is the miner's method. He crushes his ore thoroughly, and
places it in the pan with water; then, with a motion easy to learn but
difficult to describe, he swirls the water around, allowing a little
of it to escape at each revolution, carrying with it the rubbish,
until finally he has a little black sand and perhaps a few grains of
yellow substance, which is gold. Mica, or fool's gold, puzzles nobody
but the ignoramus. True, it looks like gold in certain positions and
lights, but gold will beat out thin under the hammer, just as lead
would, while mica will break up into a floury powder. Mica is very
light, while gold is very heavy; so there is no excuse for confounding
the two. If an ore contains sulphurets and gold, the latter may be
coated with some sulphur or arsenic, which would prevent the gold from
amalgamating. The only remedy for this is roasting. No single acid
will dissolve gold, but a solution known as aqua regia, made up of
three parts of hydrochloric acid and one part of nitric acid,
dissolves it. If to the solution so obtained you add some sulphate of
iron, you will get a precipitate which is metallic gold, although it
does not look like it, as it is brown in color; but if you place this
precipitate in a crucible and heat, you will get a yellow bead of pure
gold. Another test for gold is to take the solution as above obtained
and add thereto a solution of chloride of tin, when you obtain a
purple coloration that has been called the purple of Cassius.
Gold may be distinguished from all other metals by the three following
tests: It is yellow; it may be flattened by the hammer; it is not
acted upon by nitric acid.
Pure gold is soft, and the point of a knife will scratch it deeply.
Pounded in a mortar, the pulverized mineral should be passed through a
cheese-cloth screen stretched over a loop of wood. If the course
contains much pyrite, it must be roasted before washing in the pan and
amalgamating. Sample well, weigh out two pounds, put it in a black
iron pan, with four ounces of mercury, four ounces of salt, four
ounces of soda and a half gallon of boiling water. Stir with a green
stick, and agitate until the mercury has been able to reach all the
gold. Pan off into another dish so as to lose no mercury, squeeze the
amalgam through chamois leather or new calico previously wetted. The
pill of hard amalgam may be placed on a shovel over the fire or in a
clay tobacco pipe and retorted.
Gold is readily acted upon by the mixture of nitric and hydrochloric
acids known as aqua regia, or by any solution producing chlorine. Some
of the mixtures which attack it are bisulphate of soda, nitrate of
soda and common salt, hydrochloric acid and potassium chlorate, and
bleaching powder. The action is more rapid in hot than in cold
solutions, and impure gold is more easily dissolved than pure.
Mercury dissolves gold rapidly at ordinary temperatures, the amalgam
being solid, pasty or liquid. Gold rubbed with mercury is immediately
penetrated by it. An amalgam containing 90 per cent. of mercury is
liquid; 87.5 per cent., pasty; 85 per cent., crystalline. These
amalgams heated gradually to a bright red heat lose all their mercury,
and hardly any gold. About one-tenth of 1 per cent. of mercury remains
in the gold until it is refined by melting.
The veins from which the gold of the world is won do not, on an
average, hold the precious metal in greater proportion than one part
of gold in 70,000 parts of veinstone. Under favorable conditions a
proportion not one-fifth as rich as this, may yield a rich return. In
hydraulic mining on a large scale, one part of gold in 15,000,000
parts of gravel has paid a dividend.
A test known as Darton's is believed to be a valuable means of
detecting minute quantities of gold in rocks, ore tailings, etc.
"Small parts are chipped from all the sides of a mass of rock,
amounting in all to about 1/4 ounce. This is powdered in a steel
mortar and well mixed. About half is placed in a capacious test tube,
and then the tube is partly filled with a solution made by dissolving
20 gr. of iodine and 30 gr. of iodide of potassium, in about 1-1/2
ounces water. The mixture thus formed is shaken and warmed. After all
particles have subsided, dip a piece of fine white filter paper in it;
allow it to remain for a moment; then let it drain, and dry it over
the spirit lamp. It is next placed upon a piece of platinum foil held
in a pincers, and heated to redness over the flame. The paper is
speedily consumed; and after again heating to burn off all carbon, it
is allowed to cool and is then examined. If at all purple, gold is
present in the ore, and the relative amount may be approximately
deduced. This method takes little time, and is trustworthy."
Black sand, which is iron, often with some platinum and iridium,
sometimes interferes with the result of a gold assay. Attwood
recommends the following method as applicable to such a case:
"Take 100 to 1000 grains and attack with aqua regia in a flask; cool
for about thirty minutes or more; dilute with water and filter. If
gold is present, it will now be held in solution in the filtrate.
Remove the filter and evaporate the filtrates to dryness; then add a
little hydrochloric acid, evaporate and re-dissolve the dry salt in
warm water; add to the solution so formed proto-sulphate of iron;
which will throw down the gold in the form of a fine, dark
precipitate. The precipitate is seldom fine, being mixed with oxides
of iron, and must now be dried in the filter paper, and both burned
over the lamp in a porcelain dish. Then mix the dried precipitate with
three times its weight of lead; fuse, scorify and cupel. In case
platinum, iridium, etc., are found associated with the gold, an extra
amount of fine silver should be added before cupellation, and the gold
button will be found pure."
In one of his reports the State Mineralogist of California gives a
most lucid description of a mechanical assay of gold-bearing sands,
stamped ore, etc., etc. He states:
"It must be understood that this is only a working test. It does not
give all the gold in the rock, as shown by a careful fire assay, but
what is of equal importance to the mine-owner, mill-man, and practical
miner, it gives what he can reasonably expect to save in a good quartz
mill. It is really milling on a small scale. It is generally very
correct and reliable, if a quantity of material be sampled. The only
operation which requires much skill is the washing, generally well
understood by those who are most likely to avail themselves of the
instructions. These rules apply equally to placer gravels. Take a
quantity of the ore--the larger the better--and break it into
egg-sized pieces. Spread on a good floor, and with a shovel mix very
thoroughly; then shovel into three piles, placing one shovelful upon
each in succession until all is disposed of. Two of the piles may then
be put into bags. The remaining pile is spread on the floor, mixed as
before, and shovelled in the same manner into three piles. This is
repeated according to the quantity sampled, until the last pile does
not contain more than 30 pounds of ore. As the quantity on the floor
becomes smaller, the lumps must be broken finer until at last they
should not exceed one inch in diameter. The remainder is reduced by a
hammer and iron ring to the size of peas. The whole 30 pounds is then
spread out, and after careful mixing portions are lifted with a flat
knife, taking up the fine dust with the larger fragments, until about
10 pounds have been gathered. This quantity is then ground down fine
with the muller, and passed through a 40-mesh sieve. If the rock is
rich, the last portion will be found to contain some free gold in
flattened discs, which will not pass this sieve. These must be placed
with the pulverized ore, and the whole thoroughly mixed, if the
quantity is small, but if large must be treated separately, and the
amount of gold allotted to the whole 10 pounds and noted when the
final calculation is made.
"From the thoroughly-mixed sample, two kilogrammes (2000 grammes) must
be carefully laid out. This is placed in a pan or, better, in a batea,
and carefully washed down until the gold begins to appear. Clean water
is then used, and, when the pan and the small residue are cleaned,
most of the water is poured off and a globule of pure mercury (which
must be free from gold) is dropped in, a piece of cyanide of potassium
being added with it. As the cyanide dissolves, a rotary motion is
given the dish, best done by holding the arms stiff and moving the
body. As the mercury rolls over and ploughs through the sand, under
the influence of the cyanide it will collect together all the
particles of free gold. When it is certain that all is collected, the
mercury may be carefully transferred to a small porcelain cup or test
tube, and boiled with strong nitric acid, which must be pure. When the
mercury is all dissolved the acid is poured off, more nitric acid
applied cold, and rejected, and the gold is then washed with distilled
water and dried.
"The object of washing with acid the second time is to remove any
nitrate of mercury which might remain with the gold, and which is
immediately precipitated if water is first used.
"The resulting gold is not pure, but has the composition of the
natural alloy. Before accurate calculations of value are possible, the
gold must be obtained pure and weighed carefully. To purify the gold
it should be melted with silver, rolled out or hammered thin, boiled
twice with nitric acid, washed, dried, and heated to redness.
"The method of calculating this assay is simple. It will be observed
that 2000 grammes represent a ton of 2000 pounds; then each gramme
will be the equivalent of one pound avoirdupois, or one 2000th part of
the whole, and the decimals of a gramme to the decimals of a pound.
Suppose the ore yielded by the assay just described, fine gold
weighing .072 gramme, it must be quite evident that a ton of the ore
would yield the same decimal of one pound. Now one pound of gold is
worth $301.46, and it is only necessary to multiply this value by the
weight of gold obtained in grammes and decimals to find the value of
the gold in a ton of ore--$301.46 × .072--$21.70. The cyanide solution
should be kept rather weak, as gold is slightly soluble in strong
solutions of cyanide of potassium. Cyanide is a deadly poison."
Touchstones are useful in deciding the probable value of gold alloys.
Several pieces of the metal under examination are cut with a cold
chisel, and the fresh edges drawn over the touchstone. These streaks
are touched with nitric acid on a glass rod. Should no reaction
follow, the gold is at least 640 fine. Wipe the stone with soft linen
and try with test acid, made by mixing 98 parts of chemically pure
nitric acid with two parts of hydrochloric acid, adding 25 parts
distilled water by measure. If this has no effect, take a touch needle
marked 700, and make a similar streak on the stone samples. Compare,
and, if necessary, continue with the other needles, using a higher
number each time. An approximate estimate of the sample will soon be
obtained. Should the gold seem poorer than 640 fine, try with the
copper or silver needle. Practice and a good eye soon make this method
very certain in its results.
Retorted amalgam is likely to contain mercury. To test for it, put a
small fragment into a closed glass tube, taking care that it falls
quite to the bottom. Heat the gold over a spirit lamp, and a deposit
of mercury will soon be seen upon the colder sides of the tube above
the bottom. The tube may be broken and the mercury collected into a
globule under water.
In mining regions gold dust passes current as coin, according to what
is supposed to be its value. Occasionally counterfeit dust is offered.
The readiest means by which it may be detected are as follows: The
dust from any one district is always much alike, and any unusual
appearance should create suspicion. Try any doubtful pieces on a small
anvil, remembering that gold is extremely malleable. Test some of the
gold with nitric acid; effervescence or evolution of red fumes, or
coloration of the acid prove impurities to be present. Place two
watch-glasses (most useful in chemical tests) on paper; the one on a
white sheet, the other on a black, and with a glass rod convey a few
drops of nitric acid from the dish to each. To the glass on white
paper add a drop or two of ammonia; a blue color would indicate
copper. To the other add hydrochloric acid; should a white precipitate
form, it proves silver. If no action is noticed, even after heating
the dish, the dust is genuine. As "dust" is sometimes merely copper
coated with gold, the better plan is to cut all the larger grains in
two, so that the acid may attack the copper should it be present.
Copper. Copper is a very easy mineral to test for. First crush the ore
and dissolve it in nitric acid by heating. Then dilute with some
water, and add ammonia. The solution should turn dark blue. The
carbonate ores of copper do not extend deep in the mine. Their places
are taken by copper pyrites. Sulphide ores are usually difficult to
treat, and when they are to be tested it is better to roast them
before trying the tests for color.
Test for copper may also be made as follows:
The sample must be pulverized. Take an ounce of the powder, and place
in a porcelain cup. Add forty drops of nitric acid, twenty drops of
sulphuric acid and twelve drops of hydrochloric acid. Boil over the
spirit lamp until white fumes arise. When cool, mix with a little
water. Filter and add a nail or two to the liquid. The copper will be
precipitated, and may be gathered up and weighed. The amount of copper
in the sample multiplied by 32,000 will be the copper in a ton of the
ore.
Should copper be suspected, roast the powdered ore and mix with an
equal quantity of salt and candle grease or other fat; then cast into
the fire, and the characteristic flame of copper--first blue and then
green--will appear. This test is better made at night.
Coal. Coal is often more valuable than gold, and the prospector should
be prepared to estimate the value of any seams he may come across
during his travels. The following is a very rough but wonderfully
effective test for coal. Take a clay pipe, pulverize your sample,
weigh off twenty pennyweights, and place it in the bowl of the pipe.
Make a cover with some damp clay. Dry thoroughly, and put the bowl
upside down over a flame. The gas in the coal will come out through
the stem, and may be lit with a match. Let the pipe cool after the gas
has all escaped, break off the covering of clay, and if the coal was
adapted for coke the result will be a lump of that substance in the
bowl. Weigh this. The difference in weight between the coke and the
twenty pennyweights of coal that were placed in the bowl will
represent the combustible matter forced out by the heat. Now take this
coke and burn it on a porcelain dish over the lamp. You will have more
or less ash left, and the difference in weight of the ash and the coke
will be the amount of fixed carbon in the coal. Your test is complete,
and it need not have cost you even the pipe. Sulphur is a detriment to
coal, and if you notice much of it in the escaping fumes, you may be
sure your sample is not worth much.
Mercury. Cinnabar, the common ore of mercury, is a sulphide. Scratch
it with a knife, and the streak will be bright crimson. Dissolve the
ore in nitric acid, add a solution of caustic potash, and you have a
yellow precipitate. A very pretty test is to place the ore pulverized
in a glass tube with some chloride of lime; close the top of the tube,
and place a smaller one therein, so bent that it will pass into a
basin of water; heat the bottom of the tube containing the ore and
lime, keeping the upper part and the small tube cold with wet rags,
and you will have a deposit of quicksilver in the basin.
Silver. Silver ore may be detected by dissolving a small quantity in a
test tube with a few drops of nitric acid. Boil until all the red
fumes disappear. Let the solution cool, and add a little water. Filter
the whole, and add a few drops of muriatic acid, which will
precipitate the white chloride of silver. Dissolve this precipitate
with ammonia; then add nitric acid once more. Exposed to the light,
the precipitate soon shows a violet tint. Pure silver is the brightest
of metals, of a brilliant white hue, with rich luster. To detect
chloride of silver in a pulp, rub harshly with a clean, bright and wet
copper cartridge or coin, and if there be silver in the pulp the
copper will be coated with it. Graphite will also whiten copper, but
the film is easily rubbed off.
Nickel. Nickel may be determined as follows: A little of the powdered
ore taken up on the point of a penknife, and dissolved in a mixture of
ten drops of nitric and five drops of muriatic acid, should be boiled
over a lamp for a few minutes, and ten or twelve drops of water added.
A small quantity of ferrocyanide of potash will throw down a
whitish-green precipitate, indicating nickel.
Platinum. Platinum is a most refractory metal to treat, as it must be
boiled for at least two hours in the mixture of muriatic and nitric
acid, known as aqua regia. A small amount of alcohol is to be added to
the solution, and the latter filtered. The platinum is precipitated
with ammonia chloride.
Manganese. Manganese may be proved as follows: A few grains of
powdered ore are placed in a test-tube, with three or four drops of
sulphuric acid. Two or three grains of granulated lead or litharge
being dropped in, the color will become pink should manganese be in
the ore.
A preliminary examination of a mineral may be made with a pocket lens
and a penknife. With the first, any conspicuous constituents may be
recognized, while a scratch with the point of the latter will give an
idea as to the softness or hardness of the mineral. Should much quartz
(silica) be present, a sharp blow with the steel will cause sparks.
The next test should be with some ore powdered and held over a spirit
flame. A drop or two of water and a drop of sulpho-cyanide of potash
will reveal iron, should such be present, by a deep red coloration.
To another portion add one drop of hydrochloric acid, and a dense,
curdy precipitate will indicate silver, if there be any.
Added to the same original nitric acid solution, several drops of
ammonia water would detect copper by a blue color.
Antimony, tin, aluminum, zinc, cobalt and nickel, uranium and titanium
are best shown by the blowpipe.
Carbonates, that is those minerals that contain carbon and oxygen in
addition to the metal, effervesce when brought into contact with
hydrochloric acid. Some sandstones have a small amount of lime
carbonate, and must be tried under the lens, as the bubbles are
microscopic. These tests are extremely useful, but by no means
infallible, owing to so few ores being pure.
When the explorer wishes to know all the constituents of the ore he
has found, he must analyze it. An analysis gives every substance in
the ore. Such examinations may be either by the "dry" or "wet"
methods, though usually the term "analysis" is restricted to the
latter, and "fire assay" is used to describe the former. The wet assay
for silver, lead or mercury is effected as follows:
Drop a little powdered ore in a test tube; add nitric acid; dilute
with 1/8 water; warm gently over the spirit lamp. It may dissolve or
it may not. In the latter case, add four times as much hydrochloric
acid. Should all these attempts fail, a fresh sample must be taken,
and equal parts of sodium carbonate and potassium carbonate added, and
the whole strongly heated in a platinum crucible. The contents, after
cooling, is dissolved in dilute nitric acid.
In any case the assay will now be dissolved, and will be in the
solution. Filter. Pour ten drops into a test tube; add three or four
drops of hydrochloric acid. A precipitate appears. It may be silver,
lead or mercury. If silver, it grows dark violet after exposure to
sunlight, or 30 or 40 drops of ammonia dissolves it in a few moments.
Should it not dissolve, it is lead or mercury. Test for lead by
filtering, and heating some of the precipitate on charcoal before the
blow-pipe. A bead and yellow incrustation indicate lead. Should none
of these things happen, then the metal is mercury. Filter; place in
glass tubes; heat gently, and a mirror of quicksilver will appear on
the sides of the glass.
This is as far as the prospector, without the various reagents and
chemicals that the analyst has always at hand, will be able to go.
More complex treatment must be reserved until a return to
civilization.
CHAPTER III.
BLOW-PIPE TESTS.
[Illustration: BLOW-PIPE.]
As a means of readily detecting the presence of minerals in their ores
the blow-pipe, in the hands of a skillful operator, is unrivaled. Nor
is this skill at all hard to come by; two or three weeks' patient
study under a good master should teach a great deal, and subsequently
proficiency would come by practice in the field. Unfortunately, some
very clever men have become so enthusiastic as to blow-pipe work that
they have devised methods by which the amount of metal in an ore as
well as its nature may be determined, but in so doing have so enlarged
the amount of apparatus, and complicated the tests so seriously that
the simplicity of the blow-pipe outfit is in danger of being lost, and
its chief advantage of being forgotten; for there are many better ways
of determining the value of an ore. A good assay or, better still, a
mill run, is worth incomparably more than any quantitative blow-pipe
test, even when conducted by a Plattner.
The chemical blow-pipe is made of brass or German silver, with
platinum tip.
The best fuel, taking everything into consideration, is a paraffin
candle in cold climates, and a stearine candle in hot ones. Tallow may
do in an emergency, but it requires too much snuffing.
[Illustration: REDUCING FLAME.]
The blow-pipe can produce two flames. The one known as the reducing
flame, and generally printed as R.F.; and the oxidizing flame,
represented by the initials O.F. In the first the substance under
examination is heated out of contact with the air and parts with its
oxygen. In the second, it is heated in the air and absorbs oxygen.
[Illustration: OXIDIZING FLAME.]
Well-burnt pine or willow charcoal in slabs 3 inches by 1-3/4 inches
is the material upon which the mineral to be tested is placed. A small
shallow depression is scraped out of one side of it and the assay
placed therein.
Platinum wire, some 3 inches long, conveniently fused into a piece of
glass tube as a handle, is used to test the coloration of minerals in
the flame. This should be cleaned occasionally in dilute sulphuric
acid and then washed in water.
A small pair of forceps with platinum points serve a great variety of
purposes, but the beginner must be careful not to heat metallic
substances in them to a red heat, as he may thereby cause an alloy of
the metal with the platinum and spoil them for future use.
[Illustration: AGATE MORTAR.]
Glass tubing one-twelfth to one-quarter inch in diameter and from four
to six inches in length is used for a variety of purposes. From this
material what are known as closed tubes may be made by heating a piece
of the tubing at or about its center over a spirit lamp, and, when the
glass has fused, pulling it apart. These closed tubes are used in
heating substances out of contact with the air.
A small agate mortar is indispensable. It must be used for grinding
substances softer than itself to a powder, but it will break if rapped
sharply.
A small jeweler's hammer is used to flatten metallic globules upon any
hard surface A regular blow-pipe outfit would include a small anvil
for this purpose, but it is hardly necessary, as any iron or steel
surface will do.
[Illustration: MAGNET.]
[Illustration: LENS.]
[Illustration: NEST OF TEST TUBES.]
A magnet will detect the presence of any magnetic mineral, especially
if it is reduced to powder and the test made under water.
Two small files, one three-cornered and the other rat-tailed, must be
included in the list of requisites. By means of the former, glass
tubing may be notched and pulled or pushed apart, and the latter is
necessary in fitting glass tubing to the cork of wash-bottles and
other apparatus.
A good lens is indispensable. That known as the Coddington is as good
as any.
A dozen test tubes of hard glass, with stand, in small and medium
sizes, should not be forgotten.
A glass funnel 2-1/2 inches in diameter is requisite in filtering. The
circular filter papers are folded in four and placed in the funnel,
point down, three thicknesses of the paper being on one side of the
funnel and one thickness on the other.
A wash-bottle is made from a flask into which a sound cork has been
placed with holes in it for two pieces of glass tubing. The one serves
as a mouth-piece into which the operator blows, while the other,
reaching almost to the bottom of the bottle and ending in a spout
outside the cork, permits a stream of water to be forced out of the
bottle when it is blown into.
A few glass rods in short lengths do for stirrers. A little ingenuity
is better than much apparatus.
Of reagents, all those to be found in a well-appointed laboratory may
occasionally be of service, but the rough and ready prospector can get
along fairly well with the following: Carbonate of soda, borax,
microcosmic salt, cobalt solution, cyanide of potassium, lead
granulated, bone ash, test papers of blue litmus and turmeric, the
former for proving the presence of acid in a solution and the latter
that of an alkali.
The foregoing are all dry reagents. Among the wet reagents are:
Water--clean rainwater--or, better still, distilled water;
hydrochloric acid, sulphuric acid, nitric acid, ammonia, nitrate of
cobalt.
Heating a mineral with carbonate of soda on charcoal is accomplished
as follows: The pulverized mineral, intimately mixed with three times
its bulk of carbonate of soda, is placed in the cavity on the coal.
Tin ore, which is very difficult to reduce, should have a fragment of
cyanide of potassium placed upon it after it has been heated for a few
seconds, and the flame is then reapplied. A globule of metal should
result, and perhaps an incrustation on the coal. The reaction is as
follows:
Metal. Globule. Incrustation.
Gold. Yellow, malleable. None.
Silver. White, malleable. None.
Copper. Red, malleable. None.
Lead. White, malleable. Red when hot, yellow
when cold.
Bismuth. White, brittle. Red when hot, yellow
when cold.
Zinc. None. Yellow when hot, white
when cold.
Antimony. White, brittle, fumes. White.
A small loop is made at the end of the platinum wire, and it is heated
and dipped in borax; heated again, then touched while hot to the
powdered mineral and heated once more. The following colors are
obtained:
COLOR OF BEAD.
O.F. R.F. Metal.
Red or yellow, hot. Bottle-green. Iron.
Yellow or colorless, cold.
Blue, hot or cold. Blue. Cobalt.
Green, hot; blue, cold. Red. Copper.
Amethyst. Colorless. Manganese.
Green. Green. Chromium.
Violet, hot; red-brown, cold. Gray. Nickel.
The substance to be tested is generally powdered and moistened, placed
in the cavity and covered or not as circumstances may demand, with a
pinch of carbonate of soda or other suitable reagent. The following
results may be obtained:
Antimony. Place the mineral in the cavity with a little of carbonate
of soda, and blow upon it with the inner or oxidizing flame. This is
formed by inserting the blow-pipe an eighth of an inch into the flame
and blowing steadily. A white incrustation on the coal, and a brittle
button of antimony should be the result.
Lead. Treat the suspected lead ore the same way, and you will get a
yellow incrustation on the coal and a button of malleable lead.
Zinc. Proceed as above, and after blowing for a few seconds moisten
the incrustation with a drop of nitrate of cobalt. Heat once more, but
this time use the outer or reducing flame, which is produced by
keeping the point of the blow-pipe a little outside the flame and
blowing more gently than before, so that the whole flame playing upon
the coal may be yellow in color. A green incrustation will be an
evidence of zinc.
Copper. As usual, mix the ore and the soda into a paste and fuse it
with the oxidizing flame. Dig the mass out of the charcoal with the
point of a knife and rub it in the mortar with water. Now decant into
a test tube, and, allowing the sediment to settle, pour off the water.
If there was copper in the ore, red scales will be found in the test
tube.
Arsenic. Heat in the inner flame for a second or two, and if the ore
contains arsenic you will notice an odor of garlic.
Tin. This is a very difficult ore to reduce, but the addition of a
little cyanide of potash to the powdered ore will make it easier.
Fuse, after moistening on the charcoal, in the oxidizing flame, and
you will probably obtain small globules of tin.
Silver. Make a paste of the ore with carbonate of soda; add a small
piece of lead and fuse into a button. Make a second paste of bone ash
and water, and after you have dried it with a gentle flame place the
button of silver and lead on the bone ash, and turn on the oxidizing
flame. The lead will disappear, leaving a silver globule. Should it
not be pure white, but more or less tinged with yellow, it probably
contains gold; and if the button be dissolved in nitric acid, whatever
remains behind is gold.
Sometimes it is desirable to determine whether tellurium is present in
an ore. This is very easy to find out. All that is required is a
blow-pipe, alcohol lamp and a porcelain dish. Break off a small piece
of the ore, place it in the dish previously warmed, blow upon the ore
with the blow-pipe until it is oxidized, then drop a little sulphuric
acid on the ore and dish. If tellurium be present, carmine and purple
colors on the assay will proclaim the fact.
Bismuth ores are very heavy; usually they have more or less antimony
associated with them, which is a drawback, as the separation is an
expensive matter and the returns are less than they would be from a
low grade pure ore. In testing for this metal, dissolve a crushed
sample in nitric acid and then add potash in excess. If the ore is one
containing bismuth, you should have a white precipitate; if it
contains cobalt, you will get a bluish-green coloration. Bismuth is
worth about fifty cents a pound if pure and free from antimony.
Galena is often mistaken for other ores, specular iron ore for
instance. If the ore be crushed and heated in nitric acid until
dissolved, some water added, and an addition made to the solution of a
few drops of ferrocyanide of potassium, a dark blood-red precipitate
is thrown down. If the ore were galena, there would be no coloration.
The so-called steel galena which carries a little zinc is generally
richer in silver than the ordinary cube galena, though the reverse is
sometimes the case.
If lead ore be dissolved in nitric acid, the solution diluted, and
some hydrochloric acid added, a white precipitate is thrown down. Add
ammonia and the precipitate remains unaltered.
The blow-pipe operator has to learn to breathe and blow at the same
time; the breathing he does through the nostrils, the blowing is
produced by the natural tendency of the cheeks to collapse when
distended with air. A skillful operator can blow for many minutes at a
time without the slightest fatigue.
To identify cinnabar, the ore from which quicksilver is obtained, make
a paste of the substance in powder and carbonate of soda. Heat in the
open tube, and a globule of mercury will result.
Sulphur turns silver black. Make a paste with carbonate of soda, heat
on the charcoal, and removing the mass with the point of a knife lay
it on a silver coin and moisten. A black sulphide of silver should
show quickly on the coin if sulphur is present. Magnesia gives a faint
pink color when heated and treated with nitrate of cobalt on coal.
Alumina under the same circumstances give a blue color.
Roasting is an oxidizing process, the substance being heated in air,
so that it may absorb oxygen.
The test by reduction with soda on coal in the R.F. is particularly
valuable in the case of copper ore, as little as 1 per cent. being
detected.
CHAPTER IV.
ECONOMIC ORES AND MINERALS.
Aluminum is derived from two ores, cryolite and bauxite. This metal
has made rapid strides into favor during the past half-dozen years.
Although known since 1827, it remained a rare substance in the
metallic form, though it is the most abundant of any of the metals
in its ore. In ordinary clay there is an inexhaustible source of
aluminum. But the ores that yield the metal cheaply are few. Until
recently, cryolite, found abundantly in Greenland, was the chief
source of the metal, but now bauxite is used in its place. Bauxite is
a limonite iron ore in which a part of the iron has been replaced by
aluminum. It is found in Alabama, Georgia and Arkansas, as well as in
Europe. Aluminum is white, and very light in weight. It does not
tarnish easily.
The chemical composition of these ores is:
Aluminum.
Cryolite, Al{2}F{6}.6NaF 12.8 per cent.
Bauxite, Al{2}O{3}.3H{2}O 73.9 per cent.
In 1895 the production of this metal in the United States was 900,000
pounds. In 1899 it rose to 6,500,000 pounds. The only firm producing
aluminum is the Pittsburg Manufacturing Company of Buffalo, N.Y., who
reduce the metal from bauxite, which they obtain in the southern
states. One of the latest uses for this metal is for gold miners'
pans. The French seem to keep ahead of the rest of the world in
finding new uses for aluminum.
Most of the supply of cryolite comes from Greenland, where it occurs
in veins running through gneiss rocks. Glass-makers use it and pay
good prices for it. Lately makers of aluminum also buy it, as it
contains 13 per cent. of that metal.
A new aluminum-bearing mineral, discovered in New Mexico and in Ohio,
is called native alum. It gives 50.16 per cent. alumina, and may be
treated by solution in warm water, filtration, evaporation and
roasting. No estimate has yet been made of the amount available.
As bauxite promises to be in greater demand in the future than in the
present, owing to the ever-increasing demand for aluminum, the
prospector will do well to make himself thoroughly familiar with its
appearance. It is creamy white when free from iron, and the grains are
like little peas, or pisolitic. It contains water, aluminum, silica,
and generally iron. The French beds near the town of Baux are 30 miles
long and 40 feet thick. In the United States, beds have been found in
Alabama, Georgia and Arkansas. The Georgia beds are turning out
three-fifths of the bauxite produced in America. The ore is in beds
and pockets, and enough has been prospected to assure a supply for
some years to come, unless the demand should grow very decidedly, in
which case a scarcity might soon be felt. The American ore is easier
to work than the French, and manufacturers prefer it to any they can
import, even though the cost is higher and the percentage of aluminum
smaller. The Arkansas deposits are as thick as the French, and only
300 feet above the level of the tide. Imported bauxite cost $5 to $7 a
ton in New York City. American ore costs $5 to $12 a long ton. Best
selected Georgia brings $10.
Should the deposits of bauxite give out, the manufacturers of aluminum
would probably fall back on cryolite. At Tvigtuk, on the west coast of
Greenland, it exists, as a very heavy vein, in gneiss. It is
semitransparent, and snow-white. Impurities may stain it yellow or red
or even black. Its specific gravity is 2.95, and its hardness 2.5 to
3. It is fusible in the flame of a candle, and yields hydrofluoric
acid if treated with sulphuric acid. It is still used for making soda
and aluminum salts, and an imitation porcelain. It is also in general
use as a flux.
Amber. This is a fossil resin, or gum, and may often be found in
lignite beds. Recent discoveries have been made on the coast of
British Columbia that are expected to supply the world. All
pipe-smokers know it.
Antimony. The commercial ore of this metal is the sulphide known as
stibnite, or gray antimony. Its composition when pure is 72 per cent.
antimony and 28 per cent. sulphur. Hardness is 2; gravity, 4.5;
luster, metallic; opaque; gray; cleavage, perfect. Fracture,
conchoidal. Texture, granular to massive. The ore tarnishes quickly,
is easily melted, or dissolved in hydrochloric acid. The associated
minerals are generally the ores of lead, zinc, and carbonate of iron.
Baryta may be the gangue or veinstone. Antimony is worth from 10 to 15
cents a pound.
Although antimony occurs in many minerals, the only commercial source
is the sulphide, stibnite. Antimony is used as an alloy in type metal,
pewter, and babbitt metals. It is injurious to copper, even one-tenth
of one per cent. reducing the value of that metal very considerably.
The price varies greatly, being now about 10 cents a pound.
The composition of stibnite is:
Antimony.
Stibnite, Sb{2}S{3} 71.8 per cent.
The production of antimony in this country is not very large. The
output of 1899 was but 1,250 tons, valued at $241,250. The ore is
worth from $40 to $50 a ton delivered at Staten Island, N.Y.
Apatite suffered in demand when the cheap phosphates of South Carolina
were discovered, and these in turn are being ousted from the markets
of the world by Thomas slag, an artificial phosphate, and by the
easily-mined natural phosphates of Algeria. The price varies with the
quality of the rock, from $1.75 to $11 per ton, averaging in 1899,
$3.86.
Apatite is a phosphate of lime, containing 43 per cent. of phosphoric
acid. It occurs in the old crystalline and primary rocks of Canada,
but although still of some value it has yielded the position it once
occupied to the Carolina phosphate deposits, which, although not so
rich in acid, are softer, and less expensive to utilize. Apatite is
doubtless derived from the remains of animals or fishes that lived in
the distant past. The colors are often beautiful--green, pink, gray,
etc.--but the sheen is always white. Hardness of 4.8. Specific
gravity, 3.1.
Asbestos. This fibrous silicate of magnesia and lime is to be looked
for among primary rocks near serpentine dike. The fibers of this
material may be woven into cloth that will be fire-proof. It is of
considerable, though fluctuating, value.
The demand for this material is likely to increase, though at present
the supply is fully equal to demand. It is being used in Germany to
make fire-proof paper, and in Quebec to make asbestos plaster for
covering wood-work. It is generally quarried in open pits, the rock
being crushed in a rock-breaker, and the fiber freed from adhering
particles of rock and dust. It is then sorted, the longest fibers
going into the first quality heap. The production in 1899 in the
United States was 912 tons, value $13,860; in Canada, 23,266 tons,
value $598,736.
Borax. This mineral is borate of soda. Its composition is: 37 per
cent. boric acid, 16 per cent. soda, and 47 per cent. water. Its
gravity is 1.7. Hardness, 2.3. It is white, and has a sweetish taste.
Borax is valuable, but occurring as it does as an incrustation upon
the ground over large areas, a detailed description would be
superfluous, as the explorer will surely recognize it should he find
it.
Clay. A good bed of clay may be of value in an accessible region.
Brick-clay contains silica, alumina, iron, etc. Potters' clay is made
by suspending ordinary brick-clay in water, and running off the water
and fine particles suspended therein. These are allowed to settle,
and, when dry, are fine potters' clay. The better the clay, the larger
the percentage of potters' clay. Fire-clay should contain 60 per cent.
of silica, and 30 per cent. of alumina. Mixed with sand and burnt into
bricks, it will resist great heat. Light-colored clays are preferable
for this purpose, as iron is prejudicial to a good fire-brick. Kaolin
is the finest porcelain clay, and the best comes from China, Japan or
France. It is a product of decay in feldspar rocks. The potash is
washed out, and the silica and alumina left as parts of a white clay
of fine grain.
Coal. Anthracite is bituminous coal that has been subjected to great
heat and pressure; in plain language, baked. It contains over 90 per
cent. of carbon. Specific gravity 1.5 to 1.8. Hardness, 2.3 to 2.6.
The ash left after burning is white or red. There is little or no
sulphur in anthracite. It does not coke.
There are three main divisions of coal, arranged according to their
carbon, water and ash. They are:
Carbon. Water. Ash.
Anthracite 80-95 p.c. 2-3 p.c. 4-10 p.c.
Bituminous 45-80 p.c. 1-5 p.c. 8-20 p.c.
Lignite 7-45 p.c. 15-36 p.c. 6-40 p.c.
Good bituminous coal contains about 85 per cent. of carbon, but the
composition varies greatly. Cannel coal is a variety of bituminous
that gives off much gas. It burns with a bright flame in an open
grate, igniting as easily as a candle. Lignite is intermediate between
coal and peat. All the Rocky Mountain coals are lignites. It is a very
inferior coal at its worst, while at its best it is nearly the equal
of a poor bituminous coal.
Some coals will coke and others will not; nothing but a trial can
settle this matter in each individual case. Good coking coal is very
valuable.
Cobalt. Cobalt ores are always found in veins with other metals. Pure
cobalt is extremely rare. Cobalt colors are used for porcelain
painting, glass-staining, etc.
Chromium. All chrome is obtained from chromite, which contains 68 per
cent. of chrome sesqui-oxide, the remainder being iron protoxide.
Hardness, 5.5; gravity, 4.4; luster, sub-metallic; opaque. Steel-gray
to almost black. Harsh. Brittle. Cleavage, imperfect. Fracture,
uneven. Texture, massive to granular. Chromite in gravel looks like
shot. Serpentine often contains it, when it is apt to resemble a
fine-grained magnetite. It is used chiefly in iron and steel alloys,
and in making armor plate. It is also used in dyeing fabrics and in
paint manufacture. But little chrome ore is produced in the United
States. The importation in 1899 was 15,793 tons, value $18.03 per ton.
Chromite, FeOCr{2}O{3} 47-68
This ore is merchantable at $22 to $25 per ton.
Domestic ore ranges from $10 to $12 a ton, while the pure imported
ores are worth $21 a ton. The yearly consumption in the United States
is about 16,000 tons, and the American production 100 tons. This ore
is useful as a lining for furnaces, and the demand promises to become
important. Newfoundland is said to contain large deposits.
Copper. Native copper occurs in the Lake Superior region, but the
demands of commerce are supplied from chalcopyrite or copper pyrites,
and tetrahedrite or gray copper ore. Many different ores of copper may
exist in the same vein. On the surface an iron cap of gossan reveals
the deposit; immediately below may be black oxide of copper with some
malachite, lower down red oxide, and below the water-line copper
sulphides. The following are the principal copper ores:
Sp. Gravity. Hardness. P. C. Cu.
Native copper 8.8 2.8 100
Chalcopyrite 4.2 3.7 35
Enargite 4.4 3.0 48
Tetrahedite 5.0 3.5 to 4.5 35
Chalcocite 5.6 2.7 80
Bornite 5.0 3.0 55
Melaconite 6.2 2.0 to 3.0 80
Cuprite 6.0 3.6 89
Chrysocolla 2.2 3.0 45
The common ore is native copper, often associated with native silver,
the two remaining, chemically, quite distinct. Some masses of copper
occur that are too large to handle and must be cut by cold chisels, a
method that costs more for labor than the value of the metal. The Lake
Superior mines produce 140,000,000 pounds of copper a year, while
those of Montana made the gigantic output of 228,000,000 pounds in
1896. The great Anaconda mine, of Butte, is the heaviest producer,
yielding more than half the state's total.
During 1899 the New York copper market rate varied between 14.75 cents
and 18.46 cents per pound. Copper is probably abundant in the shape of
pyrites in many parts of Canada, especially in the Northwest, and
prospectors in that region should search diligently for it. The Lake
Superior mines are unique in being deposits of native copper.
Owing to the great demand for copper following upon the extraordinary
spread of electricity, copper properties have become so enormously
valuable that, possibly, the explorer will be quite as fortunate in
finding copper as in finding gold. Moreover, with the exception of
Spain and Chili, the United States has no serious rivals in copper
production,--Montana and Michigan, producing the greater part of the
output. The famous Calumet and Hecla mine, in Michigan, is now down
4,000 feet and still yields ore. The most copper ores are not
difficult to distinguish. Every one is familiar with the ruddy hue of
pure copper, the color of the native metal. It may be flattened under
the hammer or cut with the knife. A little of the ore mixed with
grease colors a flame green. Copper ores are heavy, and generally of a
bright color, either red, blue, green, yellow or brown.
Corundum. Nine hundred and seventy tons of this abrasive were produced
in the United States in 1899; value, $78,570. Corundum is found in
feldspar veins, and associated with chlorites in serpentine rock.
North Carolina furnishes half the corundum marketed. The presence of
this substance is always indicated in the South by serpentine,
chrysolite, or olivine rocks; experience being the only guide the
miners have in finding new deposits. The contacts of the olivine rocks
with gneiss usually produce rich deposits. Corundum is the hardest
substance known, next to the diamond. It is used as a polishing
powder. Emery is an impure corundum containing iron. Corundum is
composed of 53 per cent. aluminum and 47 per cent. oxygen. Specific
gravity is 4. Hardness, 9.
Feldspar. The Maine, Pennsylvania, New York, and Connecticut ores are
worth $3 to $6 per long ton (2,240 pounds) at point of production.
Fluorspar. The American market is supplied by ore from Rosiclare,
Ill., Marion, Ky., Hardin Co., Ill., and Liumpton Co., Ky., and
imported spar. It is worth $6 a ton of 2,000 pounds. This spar is
softer than quartz and of most brilliant colors, varying through the
yellows, greens, blues and reds, to pure white. The streak is always
white. Specific gravity, 3. Hardness, 4. It is worth mining when
abundant and accessible.
Gems. Gems are to be looked for in a country of crystalline rock, such
as granite, gneiss, dolomite, etc. Topaz and ruby are generally
discovered in crystalline limestones, while turquoise is usually found
in clay slate. It is not likely that the American prospector will come
upon the true oriental ruby; he will more probably find the garnet.
The ruby is next to the diamond in hardness and in value, and consists
practically of pure alumina. The garnet is but as hard as quartz, and
is a silicate of alumina with lime and a little iron. They crystallize
in different systems, the more valuable gem belonging to the
rhombohedral, and the less valuable to the isometric system.
The turquoise which has lately been found in Arizona is not a crystal.
The blue color which distinguishes it is derived from copper. It is a
phosphate of alumina with water in composition. In form it is kidney
shaped or stalactitic. Lazulite, a far less valuable substance, is
also blue, but as it crystallizes in the monoclinic system it should
not be mistaken for turquoise. Moreover, lazulite is softer and
contains magnesia and lime, which the turquoise does not. Lapis
lazuli, which is also occasionally mistaken for turquoise, belongs to
the regular or isometric system; it is commonly massive or compact,
and is a silicate of alumina with some lime and iron. It is found in
syenite, crystalline, limestone, and often associated with pyrites and
mica.
Topaz belongs to the orthorhombic system. It is a silicate of alumina
with fluorine. Powdered, mixed, and heated with microcosmic salt in
the open tube, fluorine is disengaged with its characteristic odor,
and etching action upon glass. With the blow pipe on charcoal, heated
with the cobalt solution, it gives the fine blue color of alumina.
The explorer who comes upon any hard, brightly colored stone, that may
possibly turn out a gem, should preserve it carefully until he returns
to some city, when it should be submitted to an expert. The value of a
gem depends upon so many qualities that it were hopeless for the tyro
to endeavor to arrive at any just estimate of it. He might ruin a
superb specimen, without becoming one bit the wiser. A few of the more
prominent characters of valuable gems follow:
Name. Sp. Gravity. Hardness. Color.
Aquamarine 2.7 7.7 Blue.
Emerald 2.7 7.5 Green.
Diamond 3.5 10.0 Colorless.
Garnet 4.1 7.0 Claret.
Opal 2.2 6.0 Opaline.
Ruby 3.5 8.0 Dark red.
Tourmaline 3.1 7.3 Various.
Turquoise 2.7 6.0 Blue, green.
Ultramarine 2.5 5.8 Blue to green.
Graphite. This mineral is commonly known as black lead, or plumbago.
It is the same in composition as the diamond, viz.: 100 per cent.
carbon. Specific gravity, 2 to 2.2. Hardness, 1.2 to 1.9. Color,
black. Greasy. Of value when free from impurities. Used in making
pencils, stove polish, crucibles, etc. Found in the earlier rocks.
Gypsum. A sulphate of lime occurring in great beds. Burnt, it becomes
plaster of paris.
Iron. This, the most important of all metals, is found in various
forms. The ores of iron are:
Sp. Gravity. Hardness. P. C. Fe.
Native ore 7.7 4.5 100
Magnetite 5.1 6.0 72
Hematite 4.8 6.0 70
Limonite 3.8 5.2 60
Siderite 3.8 4.0 62
Pyrite 5.0 6.3 47
Native iron is only found in meteorites that have come from space.
Magnetite is loadstone ore; the powder is reddish black, and the ore,
dark brown to black. It is found in the older rocks and is an
important ore.
Hematite varies from metallic to dull in luster. There are many
varieties of it, known as ironstone, ocher, needle ore, etc. Hematite
may be slightly magnetic. Immense beds exist in the triassic
sandstones, and in the secondary rocks below the coal measures. The
powder and streak of limonite are always yellow; it is an important
ore. Siderite assumes many forms. It is called spathic ore,
clay-ironstone, carbonate of iron, black band, etc. Most of these
carbonate iron ores only range between 30 and 40 per cent. of metallic
iron, but are in demand as fluxes for other iron ores. The pyritic
ores of iron, including marcasite, pyrrhotite and mispickel, are often
taken for gold by the inexperienced. In an accessible region pyrites
may be valuable, as they are bought by makers of sulphuric acid.
Iron is so low in price that vast deposits exist which cannot be made
use of because they would be too expensive to mine. A deep bed, or a
narrow one, or the slightest difficulty in transportation, would
preclude any profitable development. It is known that enormous areas
in northern Labrador, for instance, are full of iron deposits, yet
there seems no chance of their having the slightest economic value for
a long time, if ever. Conditions of commerce very different to those
now obtaining will have to exist before they can be utilized.
Iron ore is most favorably situated for profitable extraction when it
is near coking coal and beds of limestone; the former for fuel, the
latter for flux. Occasionally such regions as that of Lake Superior
may be able to compete successfully with others, although they do not
possess the necessary smelting facilities, because these deficiencies
are counterbalanced by inexhaustive stores of easily mined ores, and
transportation facilities unrivaled in cheapness.
Lead. The two important sources of supply are galena and cerussite.
The former contains 87 per cent. of lead, and frequently some silver
and gold. It is so distinctive as to be easily recognized. Luster,
metallic; opaque; lead-gray; harsh. Brittle to sectile (may be cut).
Cleavage, perfect. Fracture, even to sub-conchoidal. Structure,
granular or foliated, tabular, or fibrous. Specific gravity is 7.5,
and hardness, 2.6.
The carbonate cerussite contains about 79 per cent. lead. Luster,
vitreous to resinous. Translucent. Color, gray. Smooth. Brittle.
Cleavage, perfect to imperfect. Fracture, conchoidal. Massive to
granular. Rich carbonate ores look like clay, and are undoubtedly
often passed by.
The economic ores of lead are:
Lead.
Galena PbS 86.6 p.c.
Cerussite PbCO{3} 77.5 p.c.
Anglesite PbSO{4} 67.7 p.c.
Pyromorphite Pb{3}P{2}O{8} plus 1/3 PbCl{2} 75.36 p.c.
Lead ores are frequently rich in silver. They occur in limestone,
sandstone, granite and clay. The commercial ores are galena, which is
easily recognized by its steel-like cubes, and the carbonates. These
latter are like lightly colored clays when in powder and are very apt
to be overlooked. Fluor spar is as favorable a gangue for lead as
quartz is for gold.
The Rocky Mountains are the principal American sources of this metal,
but a very large amount comes from the Mississippi valley. In the
mountains the ore is a by-product, in silver smelting, being obtained
from argentiferous galena, while in Missouri, Kansas, Wisconsin and
Illinois lead and zinc are found free from any mixture with the
precious metal. The age of these deposits varies from lower silurian
or cambrian to the carboniferous.
The ore is found in limestone rocks,--sometimes in flat openings
parallel to the almost horizontal beds, or else in gash veins almost
at right angles to these. As lead is often found in dolomite
limestone, that is, limestone carrying almost as much magnesia as
lime, and this rock was undoubtedly deposited in a shallow sea,
geologists incline to the belief that therefore the lead is due to a
growth of seaweeds in whose ash this metal and zinc are known to
occur. At any rate, these deposits now have great economic value, and
the lead and zinc ore is easily got at.
Galena and zinc blende frequently resemble one another, but they may
be distinguished by this infallible sign: the powder of galena is
black, and that of blende brown, or yellow.
Lithographic Stone. This is a very fine grained compact limestone from
Bavaria. So far nothing equal to the imported stone has been found in
America. The distinguishing qualities are: Gray, drab or yellow;
porous, yet not too soft; of fine texture, and free from veins and
inequalities.
Manganese. Manganese ores in 1899 amounted in the United States to
143,256 tons, value $306,476. This mineral is used for bleaching and
making oxygen, and in steel manufacture. Pyrolusite contains 63 per
cent. manganese. Hardness, 2.3. Specific gravity, 4.8. Luster,
metallic. Opaque. Gray to bluish black. Harsh. Brittle. Cleavage,
imperfect. Fracture, uneven. Granular, massive. Manganite is harder,
4.0; its specific gravity is 4.3. Luster, sub-metallic. Cleavage,
perfect. Texture, fibrous. Wad is an impure ore of manganese found in
bogs, of little or no value.
Pyrolusite MnO{2} 63.2
Braunite Mn{2}O{3} 69.68
Psilomelane (Variable) ?
Franklinite, a zinc-manganese ore, is also a common source of supply.
An ore to be commercially valuable should contain from 40 to 60 per
cent. metallic manganese, and not over 0.2 to 0.25 per cent.
phosphorus.
To determine the value of manganese ores a somewhat intricate
calculation is necessary. Delivered at Bessemer, Pa., the Carnegie
Steel Company pays according to the following sliding scale:
Per cent. Mn. Per Unit
over 49 p.c. Fe. Mn.
46 49 p.c. 6c 28c
43 46 p.c. 6c 27c
40 43 p.c. 6c 26c
37 40 p.c. 6c 25c
34 37 p.c. 6c 24c
31 34 p.c. 6c 23c
6c 22c
Moreover, for each one per cent. of silica in excess of eight per
cent. a deduction of fifteen cents a ton is made, and a deduction of
one cent per unit of manganese is made for each 2/100 of one per cent.
of phosphorous present in excess of 1/10 per cent. From which it is
evident that there can be little profit in impure deposits of
manganese.
Mercury. Quicksilver usually occurs in the form of cinnabar, though
occasional deposits of pure metal are found in drops and small
pockets, in limestone and the softer secondary rocks, including shales
and slates. As the appearance of quicksilver must be familiar to all,
cinnabar alone needs description. Its specific gravity is 9.0; its
hardness, 2.2. It is a red brown earthy ore, the powder of which is a
dull red. It is generally found in sandstone, though it occasionally
occurs in slates, shales and serpentine. Heated gently with lime
cinnabar yields quicksilver. If copper be held over the fumes of
mercury it will be coated with a light film of the metal. An alloy
with silver has been found. Mercury is heavy, extremely brilliant, and
mobile. The composition of cinnabar is:
Per cent. Hg.
Cinnabar HgS 86.2
Although but three American states have supplied this metal, this
country has held rank as second producer. Of these California is by
far the most important. Oregon and Utah having never had any but a
small and spasmodic output. Judging by Californian experience, the
prospector is most likely to find cinnabar, the ore from which the
quicksilver of commerce is derived, in metamorphic rocks. Mercury is
always sold in flasks of 76-1/2 pounds. The production of mercury by
the United States (California) was 28,879 flasks in 1899, which were
valued at $1,155,160.
The following table shows the rock in which the most famous
Californian quicksilver mines are:
Mine. County. Rock.
Sulphur Creek Colusa Serpentine.
Abbott Lake Shale-serpentine.
Great Western Lake Serpentine. (?)
Ætna Napa Sandstone.
Corona Napa Sandstone-serpentine.
Aat Hill Napa Sandstone.
New Almaden Santa Clara Shale-serpentine.
Barton Siskiyou Shale-sandstone.
Cinnabar King Sonoma Sandstone-serpentine.
Altoona Trinity Porphyry-serpentine.
A study of the foregoing shows that serpentine is almost as intimately
connected with quicksilver as is quartz with gold, or granite with
tin. These are the things that prospectors should make a note of. With
the great increase of gold mining and the limited store of cinnabar
that is available that ore seems certain to rise in value before long.
Mica. The value of Indian mica varies from 90¢ a pound for sheets 4
in. × 1 in. to $13 a pound for sheets 10 in. × 8 in. The white mica
in large sheets is valuable. The amber-colored, and spotted, are used
for insulating purposes in electric plants, while the coarser sorts
are ground and used as lubricants, or in fire-proof paint manufacture.
Nickel. This ore is never found in metallic form, but always in
combination. Pyrrhotite, or magnetic pyrites, is the source of about
all the nickel of commerce. This ore has been already noticed under
iron. Rare but valuable ores of nickel are millerite, nickelite,
glance, and nickel bloom.
Per cent. nickel.
Millerite NiS 64.4
Niccolite NiAs 44.0
Some of the nickel of commerce is derived from nickelliferous
pyrrhotite.
Petroleum. Crude petroleum is never found in metamorphic or igneous
rocks. The stratified rocks of the Devonian, Carboniferous and
Cretaceous ages are most likely to hold it. The crude oil is almost
black, and consists of about 85 per cent. of carbon, and 15 per cent.
of hydrogen. A long iron-shod stick is all the prospector requires to
take with him in his search for surface indications of oil. The warmer
the day the easier the search, as the oil rises to the surface of the
streams, and is found in greater quantities than on cold days.
Oil existing in the lower rocks ascends through them until it
accumulates under some layer that will not let it pass through. In
this condition deep boring finds it, the rod usually tapping gas
first. Petroleum may be noticed oozing out of gravel banks, or
floating as a scum on the surface, whenever abundant. It has been
found in rocks of widely different age, from extremely ancient
formations to some that did not precede man by so very long,
geologically speaking.
Platinum. This metal is only found native. Its gravity is very high,
from 16 to 22. Hardness, 4 to 4.5. Luster, metallic. Opaque.
Whitish-gray. Smooth. Ductile. Cleavage, none. Fracture, hackly.
Texture, granular, fine. Platinum is unaffected by acids, but if
alloyed with 10 per cent. of silver it dissolves in nitric acid.
Almost infusible. Platinum occurs with placer gold in the beds of
streams. Usually it is in small grains, but one or two large nuggets
are on record from Brazil and Siberia. Serpentine rocks are believed
to have originally held the platinum found in the beds of rivers, but
none has been found in veins. The entire product of the United States
was 300 ounces in 1898; valued at $3,837. In 1899 there was none
produced.
Silver. Silver is generally found in serpentine, trap, sandstone,
limestone, shale, or porphyry rocks, the gangue being quartz, calc,
fluor, or heavy spar. All silver ores are heavy, and many of them are
sectile, i.e., may be cut with the knife. Western men test for silver
by heating the ore and dipping it into water. Some metal comes to the
surface in a greasy scum, should silver be present. Native silver is
found occasionally. Owing to the fall in value of this metal its
future is not assured. It has fallen, during the past year, once to
forty-nine cents an ounce, and this has had a most disastrous effect
upon many silver mines, forcing them to suspend operations. Should the
fall continue, as seems likely, and the price of silver go down to
forty cents an ounce, little will be produced except as a by-product
in the treatment of argentiferous lead ores.
As silver enters into chemical combination with sulphur easily, as is
seen by the black film that forms on silver articles in a room where
gas is burnt, most silver ores are sulphides. The very abundance of
silver has caused its great fall in value, and it does not appear that
it is ever likely to remain for long at a price exceeding fifty cents
an ounce, owing to the ease with which it may be produced, and the
large quantities that must find their way to market through it being a
by-product in lead smelting. From 1859 to 1891 the Comstock lode in
Nevada produced $325,000,000. This lode is a belt of quartz, 10,000
feet long and several hundred wide, and is a contact vein between
diorite and diabase. In America galena is the principal source of
silver; the chlorides and oxides rank next; while, lastly, some silver
is parted from gold when it reaches the mint, as gold always contains
more or less of that metal. No precise statement as to the manner of
its occurrence may be made since it is found in many different
positions, and is associated with all sorts of minerals. It is never
found in placer deposits, as it breaks up under the influence of
water, air, etc. Its original source is doubtless the igneous rocks,
where it occurs in association with augite, hornblende and mica.
Silver may be expected in mountainous regions of recent origin.
Between 1875 and 1891 the world's product rose from $82,000,000 to
$185,599,600. Three quarters of this came from the western hemisphere.
The commercial ores of silver are:
Silver.
Argentite Ag{2}S 87.1 per cent.
Proustite 3Ag{2}SAs{2}S{3} 65.5 per cent.
Prysagyrite 3Ag{2}SSb{2}S{3} 59.9 per cent.
Stephanite 5Ag{2}SSb{2}S{3} 68.5 per cent.
Cesargerite AgCl 75.3 per cent.
The Anaconda mine in Butte is the largest producer of silver in the
country. In 1896 its output was 5,000,000 ounces. The Anaconda is also
the heaviest copper producer in the United States, its yield of copper
being 125,350,693 pounds.
Sulphur. Brimstone is found native in the neighborhood of volcanoes,
extinct or active. It is also derived from iron pyrites. Color,
yellow. Hardness, 2. Specific gravity, 2. Luster, resinous. Smooth.
Sectile. Texture, crystalline.
Talc. The scientific name of this mineral is steatite. It contains
silica and magnesia. Its green color, pearly luster, and greasy feel,
are very characteristic. It is not attacked by boiling sulphuric acid.
Useful in the arts, but of no great value.
Tin. The composition of cassiterite, the commercial ore of tin, is
SnO{2}; equal to 78.67 per cent. of metallic tin. Cassiterite or tin
stone is a heavy ore which occurs in alluvial deposits or in the beds
of streams. It will be one of the latest ores the young prospector
will find himself able to name with certainty. Granite, with white
mica as one of its constituents, has so far always been associated
with tin. The American continent yields little tin, and it is not
likely the prospector in either the western states or in Canada will
stumble upon it, though a good deposit of stream tin would enrich him
in a short time, for the metal is in great demand. The streak, when
the metal is scratched with a knife point, is whitey-gray and very
distinctive.
Tin may some day be found in the northern Rockies, as there is plenty
of granite, which is favorable to this metal. It is worth about
thirteen cents a pound, and a vein must yield more than five per cent.
of metal to pay the cost of mining and dressing. Cassiterite, the
principal tin ore, would have to be roasted. Most of the European tin
mines were first worked for the copper they contained. The copper was
found in the capping, but as they gained in depth they became more and
more valuable for their tin. Some of the Cornish mines are
three-quarters of a mile in depth. Very lately tin has been discovered
and mined in vast quantities in the Straits Settlements, India. As it
is found in the streams the expense of mining is very light, and it is
killing the European mines. The Cornish miners put their tin ore on a
shovel when they wish to test it. The sample is first crushed fine and
a few skillful shakes get rid of all the gangue, leaving behind the
tin and wolfram. This wolfram is always associated, in Cornwall, with
the tin and it is got rid of by roasting. Australasia and Cornwall
produce most of the tin used in commerce. Tin is not found native.
Specific gravity of cassiterite is 6.5 to 7. Hardness, 6.5 to 7.
Luster, vitreous to adamantine. Translucent to opaque. Brown, black,
gray, red or yellow. Harsh. Brittle. Massive. The appearance of this
metal is so variable that nothing but a test with reagents determines
it with certainty. Granite is frequently the country rock in which tin
is found.
Zinc. This is another ore that never occurs native. Calamine or
silicate of zinc is the great producing ore. Composition: Zinc oxide,
67 per cent; silicate, 25 per cent; water, 8 per cent. Specific
gravity, 3 to 3.7. Hardness, 4.6 to 5. Luster, vitreous. Translucent.
White. Harsh. Brittle. Cleavage, perfect. Fracture, uneven. Texture,
granular crystalline. Calamine is a difficult mineral to detect
without experience, as when impure it does not look in the least like
a metallic ore. It would be taken for clay or shale. This ore results
from the decomposition of zinc blende. Blende contains 67 per cent.
zinc and 33 per cent. sulphur. It is often dark brown or black from
iron, otherwise it may be red, green or bluish. It is a troublesome
impurity in silver ores. Smithsonite is a carbonate much resembling,
and often found with, calamine. Other zinc ores are merely curiosities
and do not affect the commercial value of the metal.
In the New Jersey mines the zinc ores are the oxides zincite and
willemite, and the zinc-iron oxide franklinite. In the Missouri
region, on the other hand, sphalerite and blende are the typical ores.
Blende generally associates with the lead sulphide, galena. The Joplin
district in southwestern Missouri and the adjoining region in Kansas
are now mainly supplying the markets of the country, though the New
Jersey deposits are very valuable.
Joplin ore assaying 58 to 62 per cent. has varied greatly in price
during the past four years. The lowest quotation was $20 a ton, the
highest $51.50.
Zinc is derived mainly from the following half dozen ores:
Zinc.
Sphalerite ZnS 67.0 per cent.
Zincite ZnO 80.3 per cent.
Smithsonite ZnOCO{2} 51.9 per cent.
Franklinite (Variable) (?) 5.54 per cent.
Willemite 2ZnO.SO{2} 58.5 per cent.
Calamine 2ZnO.SiO{2}.HO{2} 54.2 per cent.
CHAPTER V.
MINING.
Although the scope of this work does not include the very complex
problem involved in the working of a great mine, prospecting and the
simpler mining operations are so intimately connected that it would
not be desirable to make mention of the one and ignore the other,
because the prospector must perforce become a miner as soon as he
discovers mineral, even though his operations should not go beyond a
shallow trial shaft.
The simplest method of hoisting dirt or rock out of a shaft, after it
has become too deep for the sinker to throw the stuff out with a
spade, is by a bucket and windlass, which may be either single or
double, according to the power required. In northwestern Canada, where
the present gold excitement has attracted so many thousand pioneers,
the miners have hitherto been content with a windlass. For their
purpose it answers well, as they sink through gravel and not more than
thirty feet at the most before reaching the bed rock. The alluvial
flats in which the coarse gold of the upper Yukon has been discovered,
are composed of gravel that is invariably frozen, summer as well as
winter, and which requires to be thawed out before it can be worked
with a pick. Strangely enough, dynamite cannot be used, as the ground
is so elastic under the frost that the tamping simply blows out and
the required effect is not produced. This peculiar condition has led
the men, who are mining in that part of the continent, to adopt
methods very similar to those used in Siberia, where, also, the ground
is permanently frozen to a great depth. After scratching the surface
of the soil, and removing the deep moss that invariably covers it,
they light large fires over night and in the morning remove the few
inches of thawed soil underneath the ashes. By this painfully slow
method they eventually sink to the richer gravel, fifteen or twenty,
or even thirty, feet below the surface, though there are few shafts of
this depth on the Klondike and the other gold-bearing creeks about
which we have heard so much. When the bed rock is reached and the few
inches of decayed surface removed, the miner builds his fire against
the side of the shaft, placing some inclined logs over it as a roof,
and goes to bed. When he awakes next day several feet of the soil have
fallen down over the logs, and this he has to hoist. It is at this
stage that the windlass worked by his companion, or partner,
demonstrates its value. In a very short time all the gravel that the
fire has thawed out is hoisted to the surface, and added to the dump,
where it must remain until the warmth of summer shall have thawed the
streams and permitted sluicing.
[Illustration: MINER'S GOLD PAN.]
A sluice is really nothing more nor less than a trough, open at the
top, in which the gold is sorted from the lighter gravel and dirt by
running water. The grade varies according to the coarseness of the
gold. Very fine gold would be carried away by too swift a current,
while coarse gold will resist almost a torrent. The sluice is built in
joints, usually a dozen feet in length; the sides may be six inches or
a foot deep, and the width varies from one to two feet. There is no
rule in this matter, but owing to the extravagant price of lumber--as
much as a hundred and fifty dollars a thousand feet, board
measure--the tendency is to make the sluices very small and very
short, thereby saving nothing but the very coarsest gold. A properly
constructed sluice should be several hundred feet in length, and the
inclination should not be more than one foot in twelve, while it may,
in a case of fine gold, be advisable to diminish this inclination by
at least a fourth. Riffles, or cross-pieces, are placed across the
sluice at intervals of a few feet, and slats are placed lengthwise,
filling up the intervals between the riffles. Into the crevices and
interstices of these obstructions the heavy gold sinks by its own
weight, and every few days, or weeks, as the case may warrant, the
miner shuts off the water by closing the gate at the head of the
sluice, removes the slats and riffles, beginning at the joint nearest
the head and working towards the tail of the sluiceway, and collects
all the gold that has accumulated.
This is a very simple form of mining, but it is not the simplest. Much
gold has been recovered from the gravel in which nature has placed it
by the aid of the pan, a sheet iron dish modeled on the housewife's
bread pan.
Next to the pan the cradle is as little complicated as anything used
in the winning of gold.
After this comes the long tom, a considerable improvement upon the
cradle, but it necessitates more water and more men.
[Illustration: HORSE WHIM.]
The horse whim is used in developing many a western prospect. The
windlass does not work well below forty feet, and where fuel and water
are to be had any sensible man will use steam power for deep mining,
but there is a gap between the windlass and the steam hoist which the
horse whim fills acceptably. To a depth of 300 feet a horse whim can
usually handle the rock and water. It is inexpensive, in the first
outlay, and costs but little to run. You can bring your bucket from a
shaft a hundred and fifty feet deep in two and a half minutes, and
with a seven hundred pound capacity in the bucket, in forty-five trips
you could raise fifteen tons a day. A shaft three hundred feet deep
would require four hours' steady work to bring to surface the same
amount. A fair speed with a one-horse whim from a three hundred foot
shaft is one hundred buckets per shift of ten hours, but the
prospector rarely has to figure on shafts of that depth. If the mine
turns out well it is likely to be in the hands of a powerful company
(of which he should be the principal shareholder) before the three
hundred foot level is reached. The weight of the horse whim is about
eight hundred pounds. It can be taken to pieces and packed anywhere
that a mule can travel; the heaviest piece will not weigh more than a
hundred pounds.
[Illustration: PROSPECTING MILL WITH HORSE POWER.]
A small stamp mill, run by horse power, is a very favorite machine
with western men, where the ore is free milling. The mortar in which
the stamps work has copper plates amalgamated with mercury inside, and
copper tables with amalgamated plates over which the pulp passes after
oozing through a fine screen in front of the mortar. These little
mills are so constructed that they can be taken apart or put together
in an hour or two. They require but one horse power and will do good
clean work up to their capacity. The following are the specifications
of a good one:
Total weight 1,500 pounds.
Weight of heaviest piece 350 pounds.
Weight of stamp 100 pounds.
Drops per minute 60 to 80.
Capacity per hour 300 to 400 pounds.
Diameter of pulley 30 inches.
Price, with horse power, about $350.
A diamond drill is a most useful adjunct to exploration of a mine or
deposit. It is, essentially, a hollow drill which may be lengthened at
will, rotating rapidly and carrying a crown of "bort" or black
diamonds at its extremity, that eats into the strata very quickly.
Holes 3,000 feet deep have been driven by the diamond drill, but such
extensive investigations of the earth's crust are tremendously costly,
and may only be undertaken by governments or rich companies. For a
depth of 700 feet, however, the expense need not exceed $2,100. The
cost of the plant for drilling would be $3,500 more. Water is pumped
down the hollow center of the drill, to keep it cool. The great
advantage of the diamond over the percussion drill is that it permits
the saving of a core, so that the character of the rocks and minerals
passed through may be known. The diamond drill does better work in
hard strata than it does in soft. The rate, in limestone, may be about
two feet an hour, down to a depth of 200 feet.
A complete outfit for boring with the diamond drill includes a steam
engine and boiler, diamond crown, lining tubes, rods, and various
minor accessories.
Hydraulic mining is the cheapest known method of recovering gold. In
four years the North Bloomfield Mining Company of California worked
325,000,000 cubic yards, which yielded only 2.9 cents of gold per
cubic yard, and realized some profit. Very poor gravel will pay when
the conditions are good. Cheap water, grades of four inches in a
hundred, ample dumping room, big banks of light gravel, large areas of
deposits, labor at a dollar a day, and a clever superintendent, make a
combination that will yield a profit out of three-cent gravel.
Miners speak of "surface" and "deep" placers; of "hill claims;" of
"bench claims" on the old river terraces; of "gulch diggings;" of "bar
claims" on the sand bars of existing rivers; of "beach sands" or those
that in a few favored localities border the ocean. A "sluice" is a
long boxway to catch the gold; a "drift" is a tunnel into the
gold-bearing gravel; and hydraulic diggings are those in which water
under pressure is used to disintegrate the gravel.
A ground-sluice is a trench cut through the bed rock. The roughness of
the natural floor serves for riffles. Booming is a process requiring a
large accumulation of water in a reservoir, which may be discharged at
once, and carry all the material that has collected below the pass,
with one full tide, into the sluices. This practice is extremely
ancient; Pliny mentions it in his Natural History.
Deep mining may be divided into drifting and hydraulic mining. In the
former the metal is won by means of tunnels and drifts or horizontal
passageways along the length of the deposit. It is usually resorted to
in districts where a flow of lava has covered the gold-bearing gravel,
and made hydraulic mining impossible. It is followed in Alaska for
another reason, viz., because the constantly frozen ground will not
permit of the more remunerative method. The gravel is carried to the
mouth of the tunnel and there dumped to be washed in the sluices. When
"cemented" it must be broken up by stamps.
Rich deep placers may be worked by drifting, but whenever practicable
hydraulicing is to be preferred as giving better results. It yields
from four to six times the amount of gold that drifting does. Thorough
exploration should precede the expenditure of large sums in a
hydraulic plant. Even should the explorations result in finding barren
gravels the money will have been well spent in saving the cost of an
unproductive plant.
Black sand (magnetic iron) almost always accompanies gold, but this
alone is no sign that gold is present, as black sand may usually be
obtained by grinding and washing crystalline rocks.
Ditches and flumes of wood or metal are used to bring the water for
hydraulic mining from the region where it was impounded in a catch
basin, often a distance of many miles. It is said $100,000,000 have
been invested in ditches and flumes, mining and agricultural, in the
western states, and new flumes are being planned every month. Some of
them consist of wrought iron pipe carried over ravines by trestles 250
feet high.
In planning a ditch the miner must see to it that his water supply is
at a sufficient elevation to command the ground. The more pressure the
water works under the better. The supply should be continuous, or at
least be available during the whole working season. Ditches in regions
of deep snow should have a southern exposure. All streams crossed by
the ditch should be diverted into it, to counteract leakage and other
loss. Waste gates must be provided every half mile. Ditches are better
than flumes. Narrow, deep, and steep ditches are to be preferred in
mountainous regions, and the reverse in valleys with soft soil. Some
Californian ditches with a capacity of 80 cubic feet per second and
grades of 16 to 20 feet per mile have been built.
[Illustration: SECTION OF DITCH.]
[Illustration: SECTION OF FLUME.]
Sometimes the face of the country requires flumes; they may even be
hung along the face of a cliff. In shattered ground and where water is
scarce flumes are better than ditches. The grade for a flume is
usually 25 to 35 feet per mile and its capacity is smaller than that
of a ditch. Pine planking 2-1/2 inches by 12 to 24 inches, and 12 feet
long, is the dimension stuff generally preferred. A flume 2 feet 6
inches square requires posts, caps, and sills of 3×4 inch; stringers
4×6 inch. Great care is needed at curves to avoid slack water and
splashing. The boxes must be shortened and the outer side wedged up
until the water flows as evenly as in the straight stretches. Should
anchor ice form the water must be shut off at once. The life of a
flume seldom exceeds a dozen years, whereas at the end of a similar
period a ditch would be carrying 10 per cent more water than at first,
owing to the sides and bottom having become consolidated.
Wrought iron pipes are employed largely in California to replace
ditches and flumes. When the pipe crosses a ravine it is known as
an inverted siphon. Piping is also used to convey water from the
"pressure box" to the "gates" and "nozzle." Wrought iron pipes have to
stand pressure varying from 34 pounds to 800 pounds to the square
inch. Air valves or blow-offs must be provided at intervals to allow
the escape of air from the pipe while filling, and to prevent a
collapse of the pipe after a break. A covering of coal-tar should be
given the pipe both inside and out. Cost varies from one dollar to two
dollars a running foot.
The pressure box ends the ditch and from it the water passes into the
supply pipe. The head of water is measured from this point. A box to
catch sand and gravel, with a side opening and sunk below the level of
the ditch, is called the "sand box."
One and a half inch plank is generally the material out of which the
pressure box is made. The depth of water in it is such that the mouth
of the pipe is always under water. A grating in front of the pipe
catches all rubbish. As no air must be allowed to get into the pipe
the water must be kept quiet and deep at the pipe-head; this is
insured by dividing the box into compartments, the first receiving the
water and discharging it through suitable openings into the second.
The water supply and the discharge should be equal. The water passes
down the feed pipe, iron gates distributing it to the discharge pipes.
Water must be turned on gradually, and the air valves must be open.
The piping terminates in a nozzle with knuckle-joint and lateral
movement. Nothing but the most secure bolting to heavy timber and the
heavy weighting of the last length of pipe should be relied upon to
keep the hydraulic giant in its place. Should it once begin bucking
every man within reach of the powerful column of water is in imminent
danger. The nozzle is directed by means of a larger deflecting nozzle,
which receives the impact of the water and causes the main nozzle to
swing right or left, up or down, as the case may demand.
A derrick capable of moving heavy boulders, and driven by water power,
is a necessity in all hydraulic mining. Masts 100 feet high and booms
90 feet long are sometimes used, the motive power coming from a "hurdy
gurdy" direct impact wheel. Experiments have shown that the bucket has
much to do with the power of the wheel. For instance, when the water
impinged against a flat bucket the efficiency of the wheel was less
than 45 per cent. of what it should have been in theory, whereas, with
the Pelton bucket, it rose to 82.6 per cent.
There is a great amount of so-called cement, or in other words
consolidated gravel, in all the northern placers, and in many
California deposits, as well. In the old Cariboo diggings on the upper
Frazer, strong companies are now pulverizing the ancient cements that
resisted all the efforts of the 59 miners with powder and stamp mill,
and are deriving large profits therefrom.
Black powder gives even better results than dynamite in gravel. The
usual allowance of powder is 20 pounds in weight for every 1,000 cubic
feet of ground to be moved. Make drifts T-shaped, and tamp the main
drift almost to the junction with the arms, which should be parallel
to the face it is required to dislodge.
[Illustration: PELTON WATER WHEEL.]
Sluices have their maximum discharge when set straight. Increased
grade may be given below any unavoidable curves with advantage, and
the outer side of the sluice must always be raised. Steps or "drops"
in the sluices help in the recovery of the gold. In general, a grade
of 6-6-1/2 inches to the 12-foot box is found best; this is equal to a
4-4-1/2 per cent. grade. Exceptional instances are on record, however,
where grades ran from 1-1/2 per cent. to 8 per cent. In a 4 to 7 per
cent. grade the water in the sluice should be 10 inches deep at least.
The following table gives useful details:
Sluice. Grade. Water.
6 ft. × 36 in. 4 to 5 p.c. 2,000 to 3,500 m. in.
4 ft. × 30 in. 4 p.c. 1,800 to 2,000 m. in.
3 ft. × 30 in. 1-1/2 p.c. 600 to 1,000 m. in.
"The longer the better," is the sluice-builder's motto. The best
"riffles" are made of blocks of pine 8 to 13 inches deep, wedged into
the bottom of the sluices. They are laid in rows separated by a space
of an inch or an inch and a half. Riffle strips keep them in position,
these latter being laid crosswise on the bottom. When worn down to
five inches, the blocks should be replaced. This amount of wear will
probably require six months. Stone and longitudinal riffles running
lengthwise of the box are often preferred.
An undercurrent is a broad sluice set at a heavy grade below the level
of the main sluice. The fine stuff drops through a grating, while the
coarse gravel continues on down the sluice.
Refuse material from quartz, hydraulic or other mines is known as
tailings. Tailings are deposited on a dump, which in the case of a
hydraulic claim must be sufficiently spacious to receive the thousands
of yards of debris deposited on it each day. When available a narrow,
deep canyon, or a tunnel, may take the places of dumps.
Quicksilver is used in the sluices, 14 to 18 flasks being used every
fortnight in a long sluice. It is not placed in the last 300 or 400
feet.
In working, keep the face of the bank "square." Washing should be
carried on continuously. Watches must be set over the sluices, or gold
is likely to be missed. As an extra precaution, the sluices should be
run full of gravel before shutting off the water. There is no fixed
custom regulating "clean ups." Some managers do so every 20 days,
others run two or three months, others again clean up but once in a
season. In large operations, the first 2,000 feet of sluice are
cleaned up every fortnight; the remaining boxes once a year.
Sluices are cleaned from the head downward, the blocks being taken up
for that purpose. The amalgam of gold and quicksilver is collected in
sheet iron buckets. The final step is reached when the amalgam is
retorted and melted in a graphite crucible.
The principle of which the hydraulic miner takes advantage is the
great specific gravity of gold as compared with water and rock. To
illustrate this quality it may be noted that on a smooth surface
inclined at an angle of 1 in 48, subjected to a heavy stream of water,
95 per cent. of the fine gold in gravel does not travel three feet.
The loss of quicksilver fed into sluices will vary, even under good
management, from 11 per cent. to 25 per cent. of the amount fed to the
boxes.
Hydraulic mines under favorable conditions are very paying
investments. Gravel yielding 10 cents a cubic yard has been worked for
6 cents a cubic yard, at the rate of a million cubic yards a year. On
another large claim 600,000 cubic yards were worked for 6 cents a
cubic yard, yielding 13 cents a cubic yard.
River dredging is another form of gold winning that has been brought
to a great state of perfection in New Zealand. Although the dredge has
not yet acquired the importance in America that was expected, it is
successful on one or two western rivers, and as the subject becomes
better understood it is conceivable that American mining engineers
will be as successful in devising improved dredges as they have been
in all other branches of their profession.
In New Zealand the bucket dredge has proved more satisfactory than the
suction dredge, although a hasty conclusion would probably give the
latter the palm. At Bannack, Mont., the Bucyrus Company has several
dredges in successful operation. One is 102 feet long, 36 feet wide,
and draws 36 inches of water. It is very substantially made, and
weighs nearly 700,000 pounds. Before such a dredge is launched, a dam
is built across the gulch to impound sufficient water. As the gravel
is dredged and washed, it is dumped astern of the dredge, which, in
the case of a shallow creek, moves up to the excavation made by the
buckets. The boilers of this dredge are double, and together have 250
H.P. There are 36 buckets, and each one has a horizontal drag of
eight feet, a capacity of five cubic feet, and travels at the rate of
fourteen feet a minute. After treatment by trommels, or revolving
screens, coppers, and sluices, and finally by a centrifugal pump, the
now almost valueless gravel goes overboard again, leaving behind 98
per cent. of the gold it once held.
The traction dredge is really a land-mining machine, as it is adapted
for work on land nearly flat, where but little water is obtainable.
The machine travels on bogie tracks. A 50-H.P. boiler supplies the
water. A boom, 40 feet long, carries a shovel of 1.5 cubic yards'
capacity, and moves 70 cubic yards each hour.
Mr. John W. Gray, one of the best authorities, has recently written to
the Mining and Scientific Press of San Francisco a most interesting
description of the progress made in saving the gold from the streams
in New Zealand. He says, in part:
"After great effort, numerous trials, many failures and some large
losses, this system of gaining gold has been evolved from crude
beginnings into a systematic and satisfactory method of mining.
Dredging for gold is now attracting attention and bids fair to become
an established form of mining for that metal. In New Zealand, where
more work of this nature has been done than elsewhere, the evolution
of the industry has been the work of years. The rivers upon which
dredging operations are carried on are swift-flowing streams, subject
to frequent floods, having a considerable depth of gravel, with
boulders and runs of pay dirt interstratified. The conditions are,
therefore, not the best for economical and successful work, and it is
not surprising that many failures have occurred. The runs of gold are,
however, often extensive and rich, and operations carried on upon such
reaches have in a number of cases given satisfactory results.
"The improved form of dredge is a double pontoon, with ladder and
chain-bucket arrangement between. Screens separate the coarse from the
fine material. Wide sluicing tables catch the gold, centrifugal pumps
supply the water, and waste material is handled by elevators. The
power is usually steam, although electricity is used in a few
instances, where conditions are favorable. The dredges vary in size
and capacity, but are now built of large size and great strength.
Twenty thousand dollars is the cost of a large dredge with all the
latest contrivances. Under favorable conditions, material has been
handled without loss that only yielded a grain of gold to the cubic
yard. The real cost in actual continued working is believed to be very
much in excess of that figure where average conditions exist.
"One dredge on the Clyde side of the Shotover, working to a depth of
twenty feet below water level, lifted 40 tons per hour when operating.
The profit on eleven dredges for the four weeks ending July 24, 1897,
was an average of $2,686 for each dredge.
"So far in this country (United States), with a few exceptions,
dredging operations for gold have not been financially successful.
From crude beginnings, however, the machines have been rapidly
improved and perfected, until now, in some localities, dredges
believed to be the most complete yet constructed are being put in
operation, and results are promised, not yet attained, in the way of
economical working and high percentage of saving. During the last few
years, a number of dredges have been operated in California, British
Columbia, Idaho, Montana and Colorado, but with poor success. Very few
prove themselves capable of paying their way. Some of the machines
were faulty within themselves, others were entirely unable to cope
with the swift currents and large boulders of the streams upon which
they were operated. This latter is said to have notably proved the
case with the dredges tried upon the Frazer and Ouesenelle rivers.
"Dredging operations on Grasshopper Creek, near Bannack, Mont., are
now carried on successfully upon a large scale. The upper Sacramento
river, in this state, has a dredge doing profitable work, and, in a
small way, dredging is successful upon the Kzamath. A dredge upon that
river, composed of two flat boats with a large steel scoop between, is
able to cut and hoist the gravel and soft bed rock, and to handle
boulders of from four to six tons' weight. The dredge is run day and
night, has a 25-H.P. engine, and requires three men for each shift.
In gravel 10 to 25 feet deep, 400 cubic yards can be handled every
twenty-four hours. Cost of dredge, $8,000.
"A large dredge of the chain-bucket variety is operating in Northern
Mexico, in a dry country, where there is little water. The actual
capacities of these machines are 60, 100 and 150 yards per hour.
"Perhaps the most interesting dredge yet brought to the notice of the
public is one lately built by the Risdon Iron Works, San Francisco,
and now operating upon the Yuba river, near Smartsville, Cal. It is of
the elevator, or chain-bucket, type, 96 feet long, composed of two
pontoons, separated by a space five feet in width, in which is
operated the ladder carrying the buckets. One man controls the dredge
by means of a power winch with six drums. Four drums carry lines from
the corners of the dredge to anchorages on shore--one a head-line and
one the ladder line. The machine is to dredge to a depth of 45 feet,
and is said to have a gross capacity of 93 cubic yards per hour. The
material discharges from the buckets into a revolving and perforated
screen. This segregates the large material, which is then conveyed
away by the tailings elevator. Water (3,000 gallons per minute) is
supplied to the revolving screen for washing and sluicing purposes by
a centrifugal pump, and the fine stuff falls through the holes in the
screen into a distributing box, from which it passes to a set of
gold-saving tables and thence to a flume. The tables are covered with
cocoa matting and expanded metal. The top tumbler of bucket-chain is
operated by a vertical compound condensing engine indicating 35 H.P.,
which also operates the pump. It is claimed for this dredge that in
any ground not deeper than 60 feet below water level or more than 20
feet above, and which contains boulders of not more than one ton
weight, the material can be handled at from 3 to 5 cents per cubic
yard. If the capacity of the machine is given without deduction for
water raised, imperfect filling and general delays, and the increase
in volume of the gravel when broken up in filling the buckets, the
actual working capacity would be less, and from these causes and the
losses from wear and tear, breakages and repairs, the cost of
operating would be increased. The cost of the dredge complete upon the
river is said to have been $25,000.
"In the evolution of the dredge into the elevator or chain-bucket
machine, now the popular form, the various kinds of dredges were given
trials. The dipper dredge is not adapted to dredging for gold, and
some of the gold is lost. With agitation of the gravel the gold soon
settles and is not recovered. It is also very difficult, if not
impossible, to construct a dipper dredge that is water-tight. Another
objection is that the material is supplied intermittently, thus making
necessary certain undesirable arrangements for supplying the material
in a continuous flow to the gold-saving tables. The same objections
apply with greater force to the clam-shell form of dredge. It is by no
means water-tight, and loses most of the gold in the act of dredging
and bringing up the gravel. The objections would seem not to have the
same force if applied to hard cemented gravel or to gravel with
sufficient clay or other binding material to make it consistent. It is
well to remember that these forms of dredges are, in many positions,
economical of operation.
"The hydraulic dredge has had fair trials and proved a failure. Large
storms greatly lessen the efficiency of this form of dredge, and
numerous boulders hamper the pumping work. The suction force, being
intense near the pipe and decreasing rapidly a short distance away,
causes the sand and gravel to be carried off, leaving the gold behind.
A centrifugal pump is therefore of little use to catch coarse gold, or
to clear a hard, uneven bottom. Cutters do not remove the trouble,
since the gravel is dispersed by the cutting, and the gold is
separated therefrom.
"These objections would not obtain under certain conditions, and it
would seem quite possible that conditions might be found existing
where the suction dredges might be arranged to do good work. A
dredging company is now constructing, at Seattle, two dredges of the
suction type to operate upon the Yukon river. This would indicate that
there are those who believe that deposits occur in and along that
river which can be successfully worked in this way.
"The chain-bucket machine, the popular form for operating under
average conditions, is a combination of the following elements: An
excavating apparatus which clears the bottom and handles the material
with little agitation and slowly and continuously delivers a regular
quantity of gravel to the gold-saving appliances; revolving screen to
receive and wash the material and separate the coarse from the fine;
an elevator or contrivance for carrying off the coarse gravel and
stones; gold-saving arrangements, or tables, over which the fine
material passes and upon which the gold is caught; a pumping apparatus
to supply water for washing and sluicing.
"The proper capacity of a machine seems to be regulated by the
capacity of the gold-saving appliances. The tables should be as wide
as possible, with frequent drops, and the fine material should be
distributed over the tables in a thin film. The tables are covered
with plush or cocoa matting, and sufficient water supplied to keep the
material clear. The material should be supplied evenly, continuously,
and regularly to the tables. Care and attention are required to catch
the fine gold. A disregard of the foregoing directions results in
great loss, more particularly in the fine gold. Mechanical skill is
required to properly design and construct a dredge, and the care of a
competent mechanic is necessary to see that the machine is kept in
order and economically operated. The saving of the gold, however, is
what makes dredging operations a commercial success. A man skilled in
these matters should be in charge of running operations. Dredges
should be built of determined capacities, and should be designed to
suit the conditions under which they are to operate. Careful
examination and investigation of the ground to be worked should be
made beforehand, and the surrounding conditions studied, and it goes
without saying that these matters require engineering skill and
experience.
"The field for dredging for gold seems large. Where the proper
conditions exist, it is a system which commends itself, and which
gives promise, in competent hands, of being an economical method of
mining. There is probably a very large extent of country where
dredging for gold will be carried on profitably. The ground need not
be in a river, if there is seepage water sufficient to float the
dredge and supply clear water for the saving of the gold. Dredging
requires little water as compared with that required for sluicing and
elevating, and this water can, in many dry localities, be supplied at
small expense, where a supply for hydraulic work or elevating would
cost a very large sum, or be impossible at any cost. Any power
suitable for driving the prime motors can be utilized to run the
dredge. Indeed, it would seem as if a system of mining was about to be
perfected which may make possible the profitable working of many
deposits not easy to be worked by other methods, and which may, in
many instances, solve problems regarding the successful working of
deposits which hitherto have seemed most perplexing and even
impossible of solution. Some doubt exists as to possible economical
dredging operations under the water of torrential streams. The strong
currents, the frequent floods, and many large boulders found in the
channels of such streams make the working of the machines difficult
and costly. This would not be so much the case in the long stretches
of less current, nor would it be so at all in the valley-like reaches
in the lower portions of rich streams, nor in the wide, flat portions
of country where the streams enter the plains."
Very few gold-bearing lodes contain nothing but free gold; on the
contrary, they carry the bulk of their values in the form of
sulphurets, having more or less gold incorporated, and even when the
gold is native and free-milling at the surface, it is generally
changed into sulphurets as depth is gained. So the miner has to
consider methods of recovery more complicated and expensive than
simple amalgamation with mercury, for upon gold included in pyrites
mercury has no effect. Titanic iron, hematite, and tungstate of iron
often hold gold, or soft clay ores carry it in their midst, and such
combinations tax all the skill of the mining engineer merely to save a
respectable percentage of the assay value. Sometimes chlorination and
sometimes cyanization are the measures tried, but supposing the
preliminary treatment to have been by stamps in the battery,
concentrating is one of the main reliances of the mill man. The
blanket table is undoubtedly the oldest type of concentrating machine,
but it is very inferior to modern inventions. Percussion tables often
do good work. In this system a sharp and frequently repeated blow is
given the table, in such fashion as to make the heavy material
separate from the light. "Shaking" and "rocking" tables are favored in
some mills, and they give better results on fine gold than any of the
previously mentioned devices. But the best machine so far invented is
the Frue Vanner--an endless rubber band drawn over an inclined table,
having both revolving and side motions. The lighter particles are
carried off by water, and the heavier collected in a trough.
[Illustration: FRUE VANNER.]
Veins, lodes, or ledges, may be found in stratified or unstratified
rocks, and in the former they generally cut the beds at an angle.
Veins are bounded by walls. The rock in which a vein is found is a
country rock. Smooth walls are called "slickensides." The upper wall
of an inclined vein is the hanging wall; the other the foot wall. A
layer of clay between the veins and wall is a selvage. A mass of rock
enclosed in the vein is a horse. The vein stone, or gangue, is all
that part of a vein that is not mineral.
[Illustration: A FAULT.]
The throw of a fault in a vein is measured by the amount of vertical
displacement. When the miner comes to a fault, he should follow the
greater angle in his attempt to recover the lode. For instance, on
mining along A B to the line of fault X Y, the exploration will be
continued downward, because the angle A B Y is greater than the angle
A B X.
Mercury that has been "sickened," that is to say, has lost its
brightness and power of amalgamating, may often be cured by washing
with an extremely weak solution of sulphuric acid and adding a little
zinc.
As regards the comparative merits of chlorination and cyanization, it
may be said the one is the equal of the other. Under certain
conditions, chlorine gives a higher percentage of gold; under others
the same may be said of cyanide. A description of either process would
be out of place, however, in a simple elementary work.
Handed down through the centuries, the primitive arrastra is still
useful in certain contingencies. It is like a cider mill in its
principle, and was probably suggested by recollections of that
machine, or else of the Spanish wine-press. A circular, shallow pit, a
dozen feet or more in diameter, is first paved with hard, uncut stones
of granite, basalt, or other hard rock. This pavement is a foot thick,
and beneath it is a bed of puddled clay 6 inches deep. A vertical
shaft with an arm, or arms, revolves in the center of the arrastra.
Grinding blocks weighing 400, or perhaps even 1,000 pounds, are
fastened to the arms by chains or rawhide strips. The forward part of
each stone is raised a couple of inches off the floor. Mule, horse,
water or steam power may be used, the speed ranging from 4 to 18 turns
a minute.
Nothing can be simpler, less expensive, or save a greater proportion
of the value in the ore than the arrastra. Its limited capacity is its
worst fault. An arrastra 10 feet in diameter will treat 500 or 600
pounds of ore at a charge, and handle one ton a day of 24 hours. Ores
that were so poor they yielded nothing to the stamp mill have paid
well with the arrastra.
This humble device may be used to advantage, probably in some of the
poorer gold-bearing cemented gravels of the Northwest. The ore should
be crushed to pigeon-egg size. Small quantities of mercury, about a
tablespoonful to every five tons of gravel, has been found a
satisfactory proportion in California.
In a permanent arrastra a layer of neatly-dressed and pointed stones
is laid in hydraulic cement. A fair-sized arrastra will require 50
pounds of quartz to charge it, and the material must be broken into
pigeon-egg size. After the machine has been started, and a little
water added from time to time, little else need to be done for four or
five hours, and this is perhaps one of the reasons for which it has
always been so favored in indolent Mexico. At this stage, the quartz
and ore will be very finely pulverized, and water should be added
until the pulp is as thin as cream. Quicksilver must now be added in
the proportion of 1-1/4 ounce for every supposed ounce of gold in the
ore being treated. Two hours' further grinding is given, and water
then admitted until the paste is quite thin, the speed of the arrastra
being reduced at the same time so as to allow the amalgam and
quicksilver to sink to the bottom. A half an hour of this treatment
suffices and the thin mud is run off, leaving the gold and amalgam on
the floor of the arrastra. A second charge of broken quartz is put in
and the operation repeated, the clean-up not taking place oftener than
every ten days, and sometimes only at intervals of a month or so. The
rougher the bottom the longer the interval between clean-ups, as all
the stone work must be taken up each time and all the sand and mud
between them must be washed carefully. The arrastra is extremely
valuable to the poor man who, having discovered a gold-bearing vein,
wishes to transfer some of the metal into his own pocket, at the least
possible outlay. Its cheapness places it within reach of all, while a
stamp will cost a good deal. Then again the amalgamation being more
perfect in the arrastra than in any other mill, it is particularly
suited for the poor, lean ores. It is, however, only adapted to those
that are free-milling, others not being suited to this form of
apparatus, nor, indeed, to any save very costly plants. Some arrastras
have been built to treat old tailings, and have paid well when water
power could be used. Free-milling gold and high-grade silver and gold
ores are those usually treated.
The flagging should be of tough, coarse rock; granite, basalt or
compact quartz are all good. This flagging should be at the very least
a foot thick. When the arms of a 10-foot arrastra are revolving 14
times a minute, the outer stone is traveling 400 feet a minute. Round
holes closed by wooden plugs, or a side gate, lets the liquid mud out.
Some mill men use chemicals in the arrastra; potassium cyanide, and
wood ashes or lye are probably the most useful, as the latter cuts
grease and the former gives life to the quicksilver. Rich silver ores
are treated with blue stone and salt. When the pulp has been ground
sufficiently, quicksilver is added, sometimes 250 pounds being put in
a single charge. A 12-foot arrastra will never treat more than two
tons a day, and often no more than one-half that. One man a shift can
look after a couple of arrastras, and the owner, in case of one
arrastra that is working on tailings, often does everything himself.
Overshot wheels, or turbines, or hurdy-gurdies, furnish the power in
many cases. A simple mule-power arrastra may be built for $150.
A side hill should be chosen for the site of a battery. Ample water
power is necessary, though provision may be made for saving it in
catch basins should such a course be desired. Moreover, there must be
plenty of room below the mill for the tailings, as it may be desirable
at some future time to put them through a second course of treatment.
[Illustration: STAMP BATTERY.]
Automatic ore-feeders are always put in by good mill men. In cold
climates the water that goes through the mill should be heated, and
this may be done by the exhaust steam, but care is necessary that no
grease get into it, as it would prevent the gold from amalgamating.
The stamps for a light mill may be 3 or 5 in number, and weigh from
700 to 850 pounds. Tables must be water-tight, with half an inch to
one inch drop to the foot, according to the fineness of the gold.
Below them tables, having the same inclination and covered with
blanketing, are used to retain specks of gold that have passed over
the plates without amalgamating.
[Illustration: THREE STAMP BATTERY.]
After the concentrated materials, always spoken of as the
concentrates, have passed over the tables, they are often roasted to
get rid of the sulphur, arsenic, etc., and afterwards treated with
quicksilver in the pan, or tin, with chlorine or cyanide. These
processes belong, however, to the domain of the professional chemist
and metallurgist, and require the knowledge and experience of an
expert to stand a chance of success.
The coarseness of the mortar screens is subject to infinite variety,
according to individual preference. The number of holes to the square
inch ranges between 60 and 800 in Australia, and between 900 and
10,000 in the United States. The holes, when round, agree in numbers
with those of sewing-machine needles, from 0 to 10. When slots are
preferred to holes, they are generally 3/8-inch in length and No. 6
diameter. Russia sheet iron, or sheet steel 1/32-inch thick is the
material of which they are made. It should weigh one pound to the
square foot, be very soft and tough, have a clean, smooth surface, and
show no rust or flaws. In Australia 1/16 sheet copper is preferred.
The holes in any case must be punched in the sheet so that the rough
edges are turned, and thus any pulp that finds its way into one of the
holes is certain to get out again and not clog. A battery may require
13 sets of screens a year; each screen having a surface of about 1-1/2
square feet. Russia iron screens endure 15 to 40 days. As the work a
stamp can do depends entirely upon how much pulp can escape through
the screen in any given time, the latter is evidently a very important
detail of a battery.
Prospecting stamp batteries differ from ordinary batteries, chiefly in
being of light build and weight.
Amalgam coming from battery stamps is often mixed with all sorts of
rubbish. After being gathered, it is dried with a sponge, foreign
matter picked off the surface and clean quicksilver added. Soft
unglazed paper thrust into the mercury removes the last vestiges of
water, and then a card is drawn vertically or a piece of blanket
horizontally across the mercury to clean it of iron. After squeezing,
the amalgam is retorted.
[Illustration: GOLD RETORT.]
All the amalgam is placed in one large kettle and, if possible, the
latter is put on a strong table having an inclined surface with a
groove and hole at the lower end to catch any stray globules of
quicksilver. Sodium amalgam, one ounce to each 75 pounds of mercury,
is put in the amalgam kettle and the whole stirred. This sodium
amalgam is not absolutely necessary, but is desirable. After some
minutes, water is poured on the mercury and the whole stirred. All
dirt rises to the surface and is removed with a sponge. The cleaning
is continued until the mercury seems absolutely free from any
impurity, when it is dried with a sponge. It is next turned into
pointed bags of stout canvas and force applied until most of the
quicksilver has squeezed through. The amalgam remains behind. The
quicksilver still contains some gold, but it had better remain if the
mercury is to be used again, as gold attracts gold; it can always be
recovered by retorting.
Sodium amalgam is best made by the miner himself, enough for one
clean-up at a time. Metallic sodium and quicksilver are the necessary
ingredients; the former being kept in a wide-mouthed bottle covered
with coal oil. A frying-pan makes a useful mixer. It must be dry and
clean. Five pounds of clean mercury is poured into the pan, and dried
with a sponge, and heated beyond the boiling-point of water, but not
much above, or there will be a sensible loss of mercury. A piece of
sodium is wiped dry, cut into 1/2-inch squares and placed with a long
pair of tongs in the center of the warm quicksilver, which, by the
way, is now off the fire and in the open air, the operator meanwhile
keeping religiously to windward of it, unless he courts salivation and
all its attendant ills. As soon as the sodium touches the mercury a
flash and mild explosion will follow, but after a few cubes have been
introduced into the frying-pan, always in the center, this will cease.
As soon as a solid mass of amalgam forms in the middle of the pan, the
contents must be stirred slowly, and a little more sodium added. The
whole mass now crystallizes out, and if put into closely-stopped
bottles it will keep without further protection for a little time.
Once opened, each bottle must be used. Observe all these directions
faithfully, then there will be no danger of inhaling mercurial fumes
nor of being blown to atoms. After the amalgam is once made, it is
safe as sugar.
In retorting amalgam never fill the flask too full, and apply the heat
gradually, and always from the top of the flask downward.
The rocker is a box 40 inches long, 16 inches wide on the bottom,
sloped like a cradle, and with rockers at each end.
[Illustration: CROSS SECTION OF ROCKER.]
A hopper 20 inches square and 4 inches deep, having an iron bottom
perforated with 1/2-inch holes, occupies the top. A light
canvas-covered frame is stretched under this, forming a riffle.
Riffles, and occasionally amalgamated copper plates, are placed in the
bottom. The gravel is fed into the hopper, the cradle being then
rocked by one hand while water is fed by a dipper with the other.
The cradle must be placed on an inclination while being worked, and
under the influence of the continued side-to-side rocking the dirt is
quickly disintegrated, passes through the riddle and falls on the
apron. From the apron it is conveyed to the inner end of the cradle
floor, from which it flows over the riffles, or bars, and out at the
mouth. The difference in level of the floor is generally about 2-1/2
inches, but this may be varied according to the nature of the dirt
treated. Large stones in the riddle or hopper must be thrown out, but
smaller ones assist in breaking up the lumps of dirt. Every little
while the pebbles are turned out and looked over for nuggets.
Clean-ups are necessary two or three times a day. The hopper is taken
off first, then the apron is slid out, and washed in a bucket or tub
containing clean water, and finally the gold and amalgam are collected
in an iron spoon from behind the riffle bars, and panned out. Gravel
requires at least three times its own weight of water to wash it. The
most convenient way is to lead the water from a stream through a pipe
discharging directly over the hopper, but this is, of course,
impracticable in some places. More often the water is led to a little
pit on the right hand side of the operator, from which he ladles it up
as required. One man can wash from one to three cubic yards daily
according to the character of the dirt, but every time he stops the
machine to feed it with gravel or to empty the riddle, the sand will
pack, and must be removed before washing can go on. Two men can wash
nearly three times as much dirt in a day as one man. But in any case,
the rocker is only a primitive machine, having a capacity but
one-fifth as great as that of the Long Tom, and but one-tenth that of
a very poor sluice, but as it is cheap, requires but little water, and
saves a high percentage of coarse gold, the rocker will continue to be
used in many districts.
The Long Tom was invented many years ago by Georgia miners.
[Illustration: LONG TOM.]
It is a trough 12 feet by 15 to 20 inches at the upper end, and 30
inches at the lower, and 8 inches deep. The grade is usually 1 in 12.
A sheet iron plate forms the lower end of the trough. These figures
refer to the upper trough. The lower or riffle-box is 12 feet long by
3 feet wide, with a fall equal to that of the trough and a sufficient
depth to keep the material and water from spilling over the sides. It
should have four riffles. For this means of saving the gold, to work
satisfactorily, the metal must be coarse and the water plentiful.
[Illustration: SLUICE BOXES.]
Every sluice is an inclined channel through which flows a stream of
water, carrying away all the lighter matter thrown into it, and
separating it from the heavy. When the operations would not be
permanent enough, or sometimes for other reasons, a ground sluice is
preferred to the ordinary box sluice made of boards. Ground sluicing
requires, however, six times as much water as does a box sluice to do
the same amount of work. It is simply a gutter in the bed rock, and if
the bottom is hard and uneven its inequalities will arrest the gold;
if not, a number of boulders too heavy to be moved by the stream are
put into the sluice to act as riffles. No mercury is used. The water
is turned off and the collected coarse gold washed in the pan.
Sluice boxes may be any length, from 30 to 5,000 feet. They vary in
width from 1 to 5 feet, though generally 16 or 18 inches. The grade is
proportioned to the fineness of the gold, varying from 8 inches to 2
feet to the 12-foot box or length. The bottom should be of 1-1/2 inch
plank, and the sides of 1-inch boards. The boxes are made 4 inches
wider at the upper end than at the lower, so as to telescope.
The best method found yet for arresting fine gold is the copper plate
amalgamated with mercury on its face. These plates are never used at
the head of a sluice or other situation where there is much coarse
gold, as they would be superfluous in such a situation, but are placed
some distance down the sluice and are most efficacious in arresting
the "flour," or excessively fine gold. Plates are always of copper
above 1/16 inch thick, and may be 6 feet or more long, and of a width
suited to the capacity of the sluice. When treated with quicksilver,
they become as brittle as glass, and must be handled with care. The
copper plate is first washed with a weak solution of nitric acid, and
then mercury that has been treated with a weak nitric acid solution is
rubbed on the plate. As this surface of quicksilver wears off, it may
be replaced by a little fresh mercury. Any green slime on a plate is
an evidence of copper salts in the water. It must be scraped off and
the spot rubbed with fresh quicksilver. Gold attracts gold, therefore
the plates should not be cleaned up too often.
Copper plates may be freed from gold by heating them over a fire and
causing the quicksilver to evaporate slowly. The plates, after being
cooled, are rubbed with dilute muriatic acid and covered with damp
cloths for one night. They are then rubbed with a solution containing
salt peter and sal ammoniac, and once more heated over some hot coals,
but not allowed to get red hot. Soon the gold scale rises in blisters;
the plates are then removed from the fire and scraped. Those parts of
the plates that have not yielded up their gold must be re-treated and
fired until they do so. All these scales of gold are then collected in
a porcelain dish, the base metals are dissolved out with nitric acid,
and the gold is then smelted. Corrosive sublimate should be placed in
the crucible as long as any blue flame is seen to come from it.
Some mill men prefer to amalgamate their copper plates with silver
amalgam, claiming that silver-coated plates save a higher percentage
of gold. To amalgamate in this way take some silver bullion, or silver
coin, and dissolve in weak nitric acid, only just strong enough to act
upon the silver. (If you use too much nitric acid you will waste
mercury and make the amalgam harder than it should be for the best
results.) After crystals have formed, quicksilver must be added,
heating gently meanwhile, until a thick, pasty amalgam has formed. Let
this new compound stand for some hours, and squeeze through chamois as
usual. The proportion of silver may be about 1 ounce to the square
foot of copper to be plated.
In facing new copper plates with this amalgam, they should be washed
first with dilute nitric acid; then in clear water; the ball of
amalgam being rubbed over their surfaces, some little force being
applied. Plates should not be used for 24 hours after coating. Porous
copper plates of the best quality, and not too heavily rolled, should
be used. Follow the amalgam with a swab, and rub the alloy well into
the plate.
Zinc amalgam (preferable when mine water containing sulphuric acid is
used in the battery) is applied to the plate after it has been cleaned
with a moderately dilute mixture of sulphuric acid and water. The
zinc-quicksilver ball is rubbed in and applied while the plate is
still wet. Zinc amalgam is prepared as follows: Cut zinc-sheet into
small pieces; wash in weak sulphuric acid; and dissolve in mercury.
When the quicksilver will take no more zinc, squeeze through chamois
and rub in. Zinc-coated plates should stand a week before being used.
Very weak sulphuric acid will always clean these plates of any scum
that may form before they have received a gold coat.
Sometimes the miner will be troubled with impure gold after retorting.
If the metal is very dark this shade may come from the presence of
large amounts of iron. A heavy proportion of mineral salts, such as
chloride of calcium (CaCl), sodium (NaCl), and magnesium (NgCl{2}),
in the battery water sometimes accounts for this. In such cases
amalgamate, retort, pulverize and roast. Then smelt with borax, the
iron passing into the slag. If necessary smelt a second time, when the
gold should be pure enough to dispose of. In extreme cases, the gold
may weigh but one-fifth of the amalgam treated.
In districts where sufficient water for sluicing is not procurable,
dry washing is resorted to. Nothing but rich, coarse gold can be
worked by this method, and the dry washer rarely delves far below the
surface for his gold. In the Mexican deserts the dirt is laid on raw
hide, all the large pebbles picked out and the sand rubbed as fine as
possible between the hands. The sand is placed in a batea and winnowed
by tossing in the air, the lighter material being blown to leaward and
the heavy gold falling into the batea. A form of winnowing machine has
been patented, which may be driven by horse or hand-power, which is
said to give satisfaction. It works by forcing a strong blast of air
from a fan through a canvas screen. The inventor claims that it will
do the work of three men, and work dirt for 2-1/2 cents a cubic yard.
When there is a tendency in the material to cake, dry washing is
impossible.
CHAPTER VI.
CAMP LIFE.
The Indian truthfully observes: "White man make heap big fire; keep
far off. Indian make little fire; get close. All same." The small fire
does best in the circular tepee tent, made of canvas or leather, in
use on the plains. The tepee is quite an institution, but it is
generally as full of smoke as a kitchen chimney, and for that reason
cannot truthfully be recommended. In theory, the smoke should all pass
out of the opening in the top.
By using no second skin and carefully excluding all air from around
the lower rim of the tepee, it will become an admirable place to cure
hams, fish, etc., by the original smoke-dried process. The Scripture
declares that he that tarrieth over the wine cup has red eyes next
morning, and so has he that sleeps in a smoky tepee. Properly made,
however, the tepee is the thing where wood is scarce.
Some original spirits are said to have started for Dawson City,
N.W.T., a few years ago with bicycles and push carts. If these means
of transport had sufficed, the world would have learnt something, as
heretofore a canoe and a sturdy pair of legs were supposed to help the
wayfarer in that region better than anything else. That is in summer;
in winter, the dog-train is the quickest mode of travel. In the
western states and in British Columbia pack horses or mules do the
most of the prospector's freighting, and in the far north he either
carries his outfit on his back or else transports it by canoe in
summer, or by dog-train after the rivers have frozen.
[Illustration: HUDSON'S BAY DOG SLED.]
No amount of written instructions will teach a man to throw a diamond
hitch, or handle a canoe in swift water. A lesson or two from an
expert will, however, set his thoughts in the right direction, and in
time he may become proficient. Canoeing, freighting and chopping are
three things that are best begun in boyhood; no one ever yet became
marvelously proficient in any one of them that began after reaching
adult age.
[Illustration: YUKON SLED AND HARNESS.]
Dog teams are made up of from three to six dogs; a full-sized team
dragging a load of 200 pounds forty miles a day for a week at a time.
In the Hudson Bay region the dogs are harnessed one behind the other,
but on the Yukon each pulls by a separate trace, and the team spreads
out like a fan when at work.
After Christmas the snow-shoe is generally a necessity in the north.
Without "paddles" on the feet the explorer could hardly make his way
through the woods, while with them on he sails along gayly, making a
bee-line over frozen lake and water courses, and taking windfalls and
down timber in his stride. The shoe in vogue in the forest is short
and almost round, and flat, while that of the plains is very long,
upturned at the toe, and narrow. There is a reason for these
modifications, as the tyro will soon find out should he substitute the
one for the other in the native habitat of either. But the loop by
which the shoe is fastened on the foot is always the same. The string
is made of moose hide; stretched, and greased before use. Caribou, or
reindeer hide, makes the best filling, but horse or bull hide will do
at a pinch. The frame is usually of ground ash, or some other tough,
hard wood.
A camp kit of cooking utensils often begins and ends with a frying-pan
and tin kettle. Certainly when traveling light, these things should be
the last to go, as with them all things are possible, even to
amalgamating and retorting the precious metals. The frying-pan must
have a socket instead of a long handle, as the latter may be cut from
a bush at any time. A low, broad kettle boils in less time than a
deep, narrow one of the same cubic capacity.
All provisions should be kept in canvas bags. Matches in a leather
case or safe, or in a corked bottle. Blankets are never kicked off if
sewn up at foot and side into a sleeping bag.
The existence of the prospector being passed in regions where the
so-called benefits of civilization have not penetrated, he is
generally a healthy, happy, hopeful man. Especially, hopeful. I do not
remember ever meeting one that was not brimful of expectation and
trust in the future. Possibly prospectors that have become pessimistic
drop out of the ranks.
Now the man who elects to dwell with nature has only himself to thank
if he does not like his lodgings. He can be comfortable or wretched,
according to his knowledge of woodcraft and wilderness residence.
Whereas the tyro starts out with the avowed intention of "roughing
it," the veteran is particularly careful to take matters as smoothly
as he may, being well assured that in any case there will be enough
inevitable discomfort in his lot to satisfy any reasonable craving. It
is just the same in other walks of life; the sailor, the trapper and
the soldier each learns to look after his own comfort and to seize
every opportunity of making life as pleasant as possible.
The three prime wants are food, clothing and shelter, and their
importance is in the order named. Now, food is something that is
painfully scarce in many parts of the world, and one of the great
problems of wilderness travel is to provide transport for the supplies
that must be carried from civilization. A rigorous northern climate
necessitates a large consumption of strong, heat-producing food, while
in the tropics the explorer gets along very comfortably with rice or
an occasional skinny fowl, with plantains for dessert, and plenty of
boiled and filtered water. Compare such a diet with that of Nansen,
the arctic explorer! He and his companion lived and waxed fat on a
diet of lean bear's meat three times a day, washed down by draughts of
melted snow water. Moreover, although government expeditions, provided
with every canned and potted luxury the stores contain, have suffered
the ravages of scurvy, these two adventurous Norwegians, living on the
food their rifles had provided, did not know what sickness meant.
Other travelers have found that they fared better by copying to some
extent the manner and customs of the natives. Fat seal blubber gives
wonderful resisting power against cold, it is said; while a mild,
unstimulating diet of rice suits the liver better under the Equator
than the Bass ale and roast beef galore.
On this continent the working man found out long ago that pork and
beans suits him nicely. The lumberman says: "It sticks to the ribs,"
by which robust, if not classical, phrase he means that he can chop
longer without feeling hungry on pork and beans than on almost any
other food. The laborer having found by experience that the side of a
pig and a sack of beans was a good combination to have in the larder,
the man of science after a couple of hundred years or so of
deliberation confirms the discovery by announcing that the flesh of a
swine mixed with the fruit of the bean contains all the
carbo-hydrates, etc., necessary to sustain life. The moral of all this
is that pork and beans must not be forgotten when outfitting. A few
other things being desirable, the following list may be consulted to
advantage by the prospective prospector. This list should suffice for
feeding one man for 12 months:
Sugar 75 pounds.
Apples (evaporated) 50 pounds.
Salt 25 pounds.
Salt pork 212 pounds.
Pepper 1 pound.
Condensed milk 1 case.
Flour 2 barrels.
Candles 1 box.
Matches 12 boxes.
Soap 1 doz. bars.
Tea 1/2 case.
Beans 200 pounds.
The dictates of fashion being unheard on the mountain side, and
beneath the pines, dress resolves itself into a mere question of
warmth and comfort. Cut is of importance truly, but only insomuch as
it allows free play to the limbs; to the arms in digging, and to the
legs in climbing the stiff side of a canyon. Home-spun, heavy tanned
duck, corduroy or moleskin, and flannel underclothing should be the
mainstays of a miner's wardrobe. Rubber boots and slickers are also
necessary to his comfort, while for winter use a heavy Mackinaw
overcoat, or even fur, for the extreme north, is advisable. When
actually at work the miner is more often in his shirt sleeves than
not, and cold indeed must the day be if an old woodsman is caught
traveling through the forest with his burly form encased in furs. For
arctic conditions akin to those found on the upper Yukon an outfit
such as the following should be chosen:
2 heavy knitted undershirts.
2 flannel shirts.
6 pairs worsted socks.
2 pairs overstockings.
1 pair miner's boots.
1 pair gum boots.
2 pairs moccasins.
1 suit homespun.
1 horsehide jacket.
1 pair moleskin trousers.
1 broad-brimmed felt hat.
1 fur cap.
1 Mackinaw overcoat.
2 pairs flannel mitts.
1 pair fur mitts.
1 muffler.
1 suit oil slickers.
2 pairs blankets.
In cold weather the feet, fingers and face require the most care. The
first should be stowed into two pairs of wool socks, and a long pair
of knee-high oversocks be drawn over these. Boots must be replaced by
moccasins. A pair of thick worsted mitts, and a pair of leather mitts
outside, keep the hands warm enough even at 20 degrees below zero. At
50 degrees below put on an extra pair--or go home until the weather
moderates.
The favorite style of architecture in the wilderness is neither Doric
nor the Gothic nor yet the Renaissance. It is called the dugout. The
beauty of the dugout is its extreme simplicity. A hole in the side of
a dry bank, a few sods or logs for roof, and there you have it. A
veteran miner goes to earth as easily as a rabbit, and, like bunny, is
never at a loss for an habitation.
Next to the dugout the log cabin deserves mention, while the wattle
and daub or 'dobe certainly secures third honors. The only drawback to
the pre-eminence of the log cabin is that to make it you must have
logs--just as the cook always insists on pigeons before she makes
pigeon pie--and logs are in some districts only known as museum
specimens. Now, the dugout or the 'dobe only require a gravel bank, or
one of those deposits of argilite that the vulgar persist in calling
clay; were it not for this fatal ease of getting, every miner and
prospector would doubtless prefer living in a snug log hut, there to
await in peace, comfort, and dignity the arrival of the representative
of the "English syndicate" to whom he is destined to sell his claim.
Napoleon found, after fighting his way across Europe and back again,
that his troops were more healthy bivouacking in the open than
sheltered in tents. In truth, the tent is a very uncomfortable and
unhealthy make-shift; cold, hot, and damp, by turns, and often badly
ventilated. A simple lean-to shelter, and a roaring fire are
infinitely preferable where wood is abundant. But it takes a lot of
wood to keep a bivouac warm on a winter's night; as much perhaps as
would feed a fair-sized family furnace for a month.
The trappers' fire is a most regal blaze. Two back logs; a pair of
"hand junks" and a "forestick" are the foundation upon which the
structure is reared, but the edifice itself often consumes a tall,
full-limbed rock maple, or a stately birch between the setting of the
sun and the rising of the same. There are three ways of making a fire;
the first is suited for a "wooden" country; the second is used by
"Lo," and other prairie travelers, where fuel is scarce.
If overtaken by storm in any wild northern region, do as the animals
and Indians do under like circumstances: seek the nearest shelter and
lie close until the weather has moderated. The secret is to conserve
your energy, not to fritter it away fighting a power against which you
may make no real headway. A shallow, brush-lined gully; the lea of a
bank, or small clump of trees; these and other seemingly slight
protections sometimes mean life instead of death. The experienced
woodsman never leaves camp without matches in his pocket; and in
winter he carries a few pieces of dry birch bark in the bosom of his
hunting shirt, as he knows how vitally necessary it is on occasions to
be able to kindle a blaze at very short notice.
A tent should never be pitched loosely, as no matter how fine the
evening the weather ere morning may be tempestuous in the extreme, and
the unpleasantness of having a tent come down about one's ears in the
dark must be experienced to be realized. Also, never pitch a tent with
the doorway toward the northwest in winter, because that is the
quarter from which comes the cold.
In summer, from June until mid-August, the mosquito, the black fly and
the midge or sand fly, make life a burden in the north. The best
remedy for the mosquito and black fly is a mixture of tar and olive
oil, of the consistency of cream, rubbed on all exposed parts of the
person. A dark green veil will also keep the insect pests out of the
eyes, mouth and ears, and in winter is better than snow goggles to
avert blindness. But, unfortunately, it interferes with the enjoyment
of the pipe, and hence is not in much favor with woodsmen.
To make good bread it is not necessary to take either yeast cakes or
mixing pan into the wilderness. An old hand thinks himself rich with a
few pounds of flour in his sack, and soon has a batch of bread baking
that would turn many a housewife green with envy. He proceeds in this
fashion: A visit to the nearest hardwood ridge shows him a green
parasitic lichen growing on the bark of the maples (lungwort). Some of
this he gathers, and steeps it over night in warm water near the
embers. In the morning he mixes his flour into a paste with this
decoction, using the bag as a pan. The dough is next covered with a
cloth and set in a warm corner to rise; a few hours later it is
re-kneaded and baked. The result should be delicious bread. Some of
the leaven, or raised dough, may be kept, and will suffice for the
next batch of bread, and so on ad infinitum.
Making bed takes longer in camp than in the city, but the result is
just as satisfactory. Nothing more comforting than a couch of fir
boughs has been devised by man. Choosing a level spot the woodsman
cuts several armfuls of the feathery tips of the fir balsam. These he
places in layers like shingles on a roof, beginning at the foot and
laying the butt of each bough toward the head. If sufficiently deep,
say a couple of feet or so, such a bed will be soft and elastic for a
night or two, when it will require re-laying. Fragrant it always is,
with the delicious aroma of the fir balsam.
The white man stretches himself instinctively feet to the fire; the
Indian just as instinctively reclines with his side to it--and his way
is the most philosophical.
Strange as it may seem, the greatest danger the wanderer runs is on
his return to civilization. Land surveyors, engineers, and others
whose work calls them into camp for months at a stretch, dread their
first night in a feather bed. They find by experience that they are
lucky if they escape with nothing more serious than a heavy cold. Hot,
stuffy air, and poor ventilation cause the trouble. Leaving the window
wide open will almost always prevent these evil consequences, and
allow the constitution to become once more tolerant of a lack of
oxygen. In the wilderness, notwithstanding, wet, cold, and exposure,
such ills as consumption, pneumonia, bronchitis, etc., are unheard of.
Boat building and net making are two arts that the prospector will do
well to master. A few weeks passed in a building yard, and a half
dozen lessons from an old fisherman will teach him all that he
requires of these simple but extremely useful accomplishments.
The best food for sustaining life in the north is pemmican. It was
once made out of buffalo meat, but now the flesh of the moose, or
caribou, or of the deer, is substituted. The meat is cut in thin
flakes and air-dried; then a mixture is made of one-third dried meat,
one-third pure haunch fat, and one-third service berries (A.
canadensis). These are rammed by main force into a bag of green hide,
and pounded until as solid as a rock. Such a solid mass of food will
keep for years in a cool climate.
Perhaps the reader may be inclined to exclaim: "Why so much about the
North; why not more about the East, South or West?" My reply to such
would be: Because the great finds of the future will surely be made in
the North. Dr. G. W. Dawson, the best authority on the subject, has
said there are 1,000,000 square miles of virgin territory in Canada
to-day, and no doubt a very large proportion of it contains mineral
deposits. This 1,000,000 square miles he divides into sixteen separate
areas, some half as large as Ireland, others half that of Europe, and
in none of them has the footfall of a white man yet been echoed.
CHAPTER VII.
SURVEYING.
A man, to make a success of prospecting, must have what is known as "a
good eye for a country." Given that faculty he will readily pick up
the little knowledge of surveying that is sometimes almost
indispensable. A tape measure, and a prismatic or surveying compass,
are all that he is likely to require in laying off to his own
satisfaction the extent of his claim, or any similar simple operation.
The surveying compass has two fixed sights, and a Jacob staff
mounting, into which a wooden support is inserted. The north end of
the compass is always pointed ahead, while the needle, which of course
indicates the magnetic north, gives the bearing of the line run toward
that north. Now, magnetic north is not by any means the same thing as
true north, in fact in very few localities on the earth's surface are
they the same, and then never for long. In the extreme east of the
United States the needle points some twenty degrees to the west of
true north, and in Alaska it points thirty-five degrees to the
eastward of it. There is therefore one meridian somewhere in the
central valley where the true north corresponds with the magnetic
north, but as the magnetic pole is always shifting this never remains
true of the same meridian for long.
[Illustration: SURVEYING COMPASS.]
When there is no local magnetism from iron ores, or rocks containing
magnetite, the needle is fairly reliable, though never perfectly
accurate, but when such attraction exists the compass is
unsatisfactory. Such areas of attraction, however, are usually
limited, and by squinting back, taking what is known as a "back
sight," a local attraction may be detected, and in that case ranging
by rods must be resorted to until the compass needle once more seeks
its true position. To range by rods the course of the line having been
determined by retracing the route followed to the last reliable mark,
a stake is driven in at that point, and the surveyor standing some
little distance behind it on the correct line directs an assistant to
place another rod in such a position that the first hides it from
view. It will then be on a prolongation of the line, and this
operation being continued the surveyor will, in due time, find himself
beyond the reach of the local attraction that deflected his needle and
can resume compass work.
A chain is 66 feet long. Oftentimes in mountainous or brush-covered
countries a half chain of 33 feet, made of light wire links, is
preferred. Two men do the chaining, which could of course be done by
means of an ordinary tape measure in an emergency, the leader carrying
ten pins of iron or wood, and the rear man taking one up as each chain
is measured off. When all are used, ten chains (1/8 mile) have been
covered. The men exchange pins and the tally man, usually the hind
chainman, calls out "Tally one," and cuts a notch in a stick. Careful
chaining is the essence of good surveying. The chain must always be
kept horizontal, or else an allowance made for the inclination at
which it was held when the measurement was taken, otherwise the
results will be misleading, for all surveyors' measurements of areas
are theoretically on a flat surface.
To ascertain the height of a tree, tower, etc., fold a square of paper
across, and glancing along the hypothenuse (longest side) of the right
angle so found, ascertain at what point your line of sight just
catches the top of the object. Then its height is the same distance as
the distance from where you stand to its foot, or the length of a
plumb line falling from its summit, together with the height of your
eye above the ground, added.
[Illustration]
Another method is to measure the shadow of the object on a level
surface, next measure your own. Then
As your shadow is to your height so is the shadow of the object to
its height.
The area of a square is equal to the square of one of its sides.
The area of a triangle is equal to the base multiplied by half the
height.
The areas of figures containing more than three sides may always be
found by resolving such figures into a series of right angled
triangles.
Very frequently the surveyor is called upon to measure an inaccessible
line. There are many ways of solving such a problem, but one of the
simplest is as follows:
[Illustration]
Supposing the required distance is that from bank to bank of a river
(Y-X). Then lay off the base line Y-M, driving stakes at each end;
make M-P at right angles to Y-M. Sight from P to X, and drive in a
stake at Z. Then:
Z M : M P :: Z Y : Y X.
While these simple surveying problems are easily solved, the
prospector should never forget that mine surveying requires skill,
experience and accuracy. He will do well always to call in the service
of a mining engineer should his "prospect" ever become a full-fledged
mine, as little errors of direction are particularly costly mistakes
when they occur underground.
Should you wish to lay off a certain acreage as a square, proceed as
follows:
As there are ten square chains to one acre, multiply the content in
acres by 10 to reduce to square chains. Then find the square root of
this number of square chains, and that will be the length of a side of
the square required. For instance:
To lay off 25 acres as a square:
25 times 10 equals 250 square chains.
Whose square root is 15.81.
Ans. The plot must be 15 chains 81 links square.
Seventy average paces is almost exactly equal to the side of a square
acre.
If you know the content and length of one of the sides of a
rectangular figure it is easy to lay it off. Thus:
Given a claim 10 chains long, how wide must it be to cover 5 acres?
5 times 10 equals 50 square chains.
10 divided by 50 equals 5.
Ans. 5 chains wide.
CHAPTER VIII.
FLOATING A COMPANY.
Should the prospector discover mineral that increases in amount as the
mine is opened, and shows that it is likely to prove a profitable
deposit, he will have little difficulty in selling out to some wealthy
syndicate. But if his mine is likely to become a big producer he
should try rather to organize a company, of which he should be a
shareholder--the controlling one if possible--as then the output of
the mine will probably make him a rich man. It is rare that a
prospector selling outright obtains anything but a fraction of the
value of a good mine. Nor is it reasonable to suppose he should. When
he sells, the profits of the buyers are all in the future, and may
never materialize. They take all risk, and consequently insist upon a
bargain.
The more money a prospector can invest in the development of a good
mine the better price he is likely to get when he sells. Business men
dearly like to see great masses of ore in the shafts and cuts, and are
always more willing to pay a handsome price when they know something
distinctly promising about the purchase.
Let the prospector, therefore, lay open his prospect as thoroughly as
he can with the means at his disposal, and if he has faith--as he
should have--in the mine he is selling, let him take a good big block
of stock in part payment.
He must see to it, too, that sufficient working capital is provided,
as there are very few mines that pay expenses from the start.
Sometimes, when the shareholders are very timid, and but little money
has been paid into the treasury in the first instance, they become
restive after a call or two and refuse to honor further demands. This
has been the ruin of many a promising venture.
Supposing, however, that this mistake has been avoided, and that
sufficient funds are in the treasury to meet all likely, legitimate
drains upon it, the question of officers remains a weighty one. The
board of directors should be level-headed, shrewd men, with
common-sense, business ideas; the secretary should understand his
work; and the mining engineer placed in charge of the mine should be
one whose professional knowledge is equal to the demands of the
position. The secretary must have such a knowledge of the proper price
of labor, and material, as to detect any extravagance on the part of
the manager.
At least one member of the board of directors should understand
mining. Good salaries paid to the mining engineer or manager, and to
the secretary, will be money well spent, provided they are competent.
Cheap men have no business in such responsible positions, where the
handling and wise expenditure of large sums of money necessitate
brains and special training.
As to the mine manager, he should be a miner, surveyor, metallurgist,
assayer, bookkeeper and half-dozen other things rolled into one, and
that one an honest man. Very low grade ore would probably pay in the
hands of such a paragon of perfection--but he must be sought for long
and diligently, and even then he may not be found.
New processes are to be shunned until they have proved their worth and
ceased to be new. No sooner is a mine floated than all sorts of knaves
and fools appear on the scene, with new and wonderful appliances for
saving 99.9 per cent. of all the value in the ore. Be rude to them.
Drive them away with sticks and stones if necessary, but as you value
your salvation do not hearken to them. Let some one else do the
experimenting; when you know a process is good, the time will have
come to spend money on it. There are at the present moment thousands
of tons of costly machinery rusting in lonely Rocky Mountain canyons
that were in their day "novelties," warranted to save all the values
in the ore, while the unfortunate shareholders, whose misspent money
freighted these things to their final resting place, are now,
perchance, "touching" the belated Chicago or New York pedestrians for
a nickel.
The only real guide to the economic value of an ore is the treatment
of a large bulk of it in the mill.
Plenty of ore should be kept blocked out ahead of the workings. The
more ore in sight the better for the future of the mine.
Lastly, remember that thieving sometimes takes place on rather a large
scale, and be on the watch to detect it.
But there is a bright side to mining as well as a dark, and those
fortunate men who paid 3, 5 or 8 cents for the stock of a mine that
now sells for $7 can see it quite plainly; and there are many such.
Mining is not a gamble as some would have the world believe, but a
legitimate occupation, demanding great nerve and skill, and sometimes
great patience, but not infrequently rewarding the possessors of these
admirable attributes by wealth almost inexhaustible.
CHAPTER IX.
MEDICAL HINTS.
Miners as a rule are a healthy, hardy lot of men, but nevertheless
they are occasionally taken ill, and there is very seldom a doctor
near at hand. Moreover, by the very nature of their work they are
particularly liable to accidents.
The so-called miner's consumption is caused by want of fresh air. The
miner passes most of his life in places where there is a great
deficiency of oxygen. Deep down in the mine the air is usually very
bad, being full of smoke and damp, and the hut in which he sleeps is
too often overcrowded, while the places in which he seeks his
amusement, should he live in a mining camp, are usually little better.
The remedy for this state of affairs is to get all the fresh air
possible, then consumption is not to be feared.
Should poison have been swallowed, an emetic ought to be given as
quickly as possible. Mustard, or salt and warm water, are tolerably
efficacious, but a dose of 60 grains of ipecac is more effectual.
While the emetic is acting, the patient should drink freely of warm
water or warm milk.
In case of apparent drowning the body should be stripped down to the
waist, rapidly dried, placed on a flat surface with the head and
shoulders raised a little, and hot bricks applied to the feet.
Breathing should be imitated by raising the arms above the head and
turning the body on its side; turn the body back on the face and press
the arms down to the side. Do this about sixteen times a minute, and
keep it up half an hour if necessary.
In case of a wound which bleeds freely, a distinction must be made
between blood issuing from a vein and blood issuing from an artery. In
the first instance, it will be nearly black, or at least very dark; in
the second, it will be bright red and spurt forth. When from a vein,
bleeding must be controlled by pressure below the wound, that is,
farther away from the heart, while in the case of an artery, which is
always more dangerous, immediate pressure must be made above the wound
on the line of the artery between the wound and the heart. A pebble
rolled up in a handkerchief and tied around the limb, with the stone
directly above the artery, and tightened by twisting a stick in it, is
a good rough-and-ready means to stop bleeding. Sometimes a pad should
be placed between the handkerchief and the artery.
Anything that excludes the air, such as wheat flour, or olive oil, or
boiled linseed, or grated raw potato, is good to spread over a burn.
If any considerable surface is burned the patient is in great danger,
but small burns are rarely fatal, although they may be very painful.
The best application of all is linseed oil and lime water.
Scurvy is a disease that is very much to be dreaded whenever fresh
meat and vegetables are scarce. It is now thought to be a condition of
acid-poisoning, and the remedy is alkaline salts, such as carbonate of
soda or carbonate of potash. Lime juice is also an anti-scorbutic. In
cold weather a diet of almost exclusively fresh fat meat will keep off
scurvy.
Pneumonia is usually most fatal in crowded camps, where the men do not
get a sufficient amount of pure, fresh air.
CHAPTER X.
DYNAMITE.
Dynamite should be stored in a magazine which must be dry, cool, and
well ventilated. Bricks are best, but when built of wood, the frame
should be covered inside and out with boards allowing the air to have
free circulation between the walls, so that the inner wall may not be
heated by the sun.
Do not store your caps with your dynamite.
If powder was well made, it is as good a dozen years afterwards as it
was on the day it came from the mill.
Most accidents occur in thawing dynamite. Dynamite freezes between 40
and 45 degrees Far., that is, 10 degrees above the freezing point of
water, and although it does not explode, if heated slowly, until 320
degrees Far. is reached, yet the quick application of dry heat may
explode it at 120 degrees Far. This makes it so dangerous, for a stick
of powder hot enough to explode under certain conditions may be held
in the hand with little inconvenience. Powder should be thawed by
placing it in a water-tight vessel and the vessel set in hot water. It
should never be placed on or under a stove, or in an oven, or on a
boiler wall to thaw out, as is so often done by the unthinking. Frozen
dynamite is especially liable to explode from heat quickly applied.
Nevertheless, reckless men will continue to blow themselves to pieces
by foolhardy carelessness.
Frozen powder is unfit for use. It will burn or smoulder, and some of
it may be left in the drill hole to explode when it is not wanted to.
CHAPTER XI.
ATOMIC WEIGHTS.
The atomic weight of a mineral is the proportion in which its elements
are united, i.e., they represent the weights of the different atoms
in the minerals. Hydrogen, being lightest, is made the unit.
Supposing it becomes desirable to find the proportional weights of the
elements of any substance with a known chemical formula. Multiply the
atomic weight of each element by the number of atoms of such element,
and add these products together; this will give the weight of all. The
proportion of each is arrived at by a simple calculation.
For instance: How much metallic silver is there in 100 pounds of
Argentite, or silver glance, whose composition is Ag{2}S?
Then
Ag equals 108 times 2,--216.
S equals 32 times 1,--32.
So that in every 248 pounds of the glance there are 216 pounds of
metallic silver, and by proportion we find its percentage is 87.1.
The following tables give the symbols, atomic weights and specific
gravities of certain abundant elements. Rare elements are omitted:
Symbol. At. Wt. Sp. Gr.
Aluminum Al 27.5 2.56
Antimony Sb 122.0 6.70
Arsenic As 75 5.70
Barium Ba 137 4.00
Bismuth Bi 210 9.7
Calcium Ca 40 1.58
Carbon C 12 3.50
Chromium Cr 52.5 6.81
Cobalt Co 58.8 7.70
Copper Cu 63.5 8.96
Gold (Aurum) Au 196.77 19.30
Hydrogen H 1.0 0.069
Iodine I 127.0 4.94
Iron (Ferrum) Fe 56.0 7.79
Lead (Plumbum) Pb 207.0 11.44
Manganese Mn 55.0 8.1
Mercury (Hydrargyrum) Hg 200 13.59
Nickel Ni 58.8 8.60
Nitrogen N 14.0 0.972
Oxygen O 16.0 1.105
Phosphorus P 31.0 1.83
Platinum Pt 197.4 21.53
Potassium (Kalium) K 39.0 0.865
Selenium Se 79.5 4.78
Silicon Si 28.0 2.49
Silver (Argentum) Ag 108.0 10.05
Sodium (Natrium) Na 23.0 0.972
Sulphur S 32.0 2.05
Tellurium Te 129.0 6.02
Tin (Stannum) Sn 118.0 7.28
Zinc Zn 65.0 7.14
CHAPTER XII.
ODDS AND ENDS.
MINER'S INCH.
A miner's inch of water varies in different States, and is, therefore,
not a fixed quantity. In some States it means the quantity of water
that will flow through an orifice one inch square on the bottom or
side of a box under a pressure of four inches. Under these conditions
a miner's inch will discharge 2259 cubic feet, or 17,648 gallons every
twenty-four hours, which is at the rate of 12 gallons a minute. Fifty
of these miner's inches are equal to a cubic foot of water discharged
every second. One cubic foot of water a second would be sufficient to
supply the wants of seven thousand city dwellers.
In calculating the amount of water required by a stamp mill it is
usual to allow 72 gallons for every stamp, 120 gallons for every pan,
75 gallons for every settler, 120 gallons for every Fruevanner, 30
gallons for a concentrator, 350 gallons for a jig, and 7-1/2 gallons
for every horse-power of a boiler each hour. If the water after
passing through the mill is impounded and used over again, the loss
will be about 25 per cent.
LUMBER IN A LOG.
To Find: Multiply the diameter in inches at the small end by one-half
the number of inches, and again multiply this product by the length of
the log in feet; this product divided by 12 will give the number of
feet of one-inch boards the log will make.
HORSE-POWER OF BOILERS.
For horizontal, tubular and flue boilers, divide the number of feet of
heating surface by 15; this will give the horse-power. A cord of pine
wood weighing 2,000 pounds is about equal to 1,000 pounds of soft coal
for steam purposes. Each foot of grate should burn 20 pounds of soft
coal, or 40 of wood, per hour, with a natural draught.
HORSE-POWER OF AN ENGINE.
Multiply the area of the cylinder in square inches by the average
effective pressure in pounds to the square inch, deducting three
pounds per square inch for friction. Multiply this remainder by the
speed of the piston in feet per minute, and divide by 33,000. The
quotient will be the true horse-power.
HORSE-POWER OF PELTON WHEEL.
The Pelton wheel is in high favor with California miners. When the
head of water is known in feet, multiply by 0.0024147 and the product
is the horse-power that one miner's inch of water will give.
ASSAYING.
The muffle furnaces of the Morgan Crucible Company of Battersea are
favorably known. The most useful size is that taking a "D" Muffle,
8-1/2 inches by 5 inches by 3-1/4 inches.
A CHEAP "TESTING" OUTFIT.
Sometimes the pioneer is forced to attempt a good many investigations
with very simple apparatus. Should he possess the following, he can
achieve much: A spirit lamp, candle, blow-pipe, magnet, a bottle of
hydrochloric acid, quart glass jar, three test tubes with corks, two
feet of glass tubing (hard glass), copper wire, two square inches of
tin plate, forceps and test paper. Such an outfit could certainly be
bought for $1.
WEIGHT OF EARTH, SAND, GRAVEL, ETC.
A ton of shingle averages 23 cubic feet.
A ton of pit sand averages 22 cubic feet.
A ton of earth averages 21 cubic feet.
A ton of river sand averages 19 cubic feet.
A ton of coarse gravel averages 19 cubic feet.
A ton of clay averages 18 cubic feet.
A ton of marl averages 18 cubic feet.
A ton of chalk averages 14 cubic feet.
WEIGHTS OF ORES AND ROCKS.
Quartz, 162 pounds a cubic foot; silver glance, 455 pounds; ruby
silver, 362; brittle silver, 386; horn silver, 345; antimony glance,
287; cinnabar, 549; copper pyrites, 262; gray copper, 280; galena,
461; zinc blende, 249; iron pyrites, 312; limestone, 174; clay, 162.
CALIFORNIA PUMP.
A very useful pump, in regions where transportation is a problem, is
the California pump. It is a rough chain-pump. A box 10 inches by 3
inches, inside measurement, and 10 feet to 30 feet in length,
according to requirements, forms a tube reaching from the water to be
removed to the level at which it is to be discharged. In this an
endless band of stout canvas or leather works, passing under a roller
at the lower end, which is immersed in the water. At the higher end
the belt passes around a drum worked by water, horse, or manual power.
On the belt are wooden or metal projections that fit the box, forcing
the water upward as the drum revolves.
HYDRAULIC DATA.
The prospector, and more especially the miner, will do well to commit
the following figures to memory:
An Imperial gallon of water weighs 10 pounds.
Gallons multiplied by .1606 equals cubic feet.
Cubic feet multiplied by 6.288 equals gallons.
Gallons multiplied by 277.46 equals cubic inches.
Cubic inches multiplied by 0.003604 equals gallons.
Cubic feet multiplied by 62.8 equals pounds.
Pounds multiplied by .0166 equals cubic feet.
Gallons multiplied by 0.004464 equals tons.
Tons multiplied by 224 equals gallons.
Tons multiplied by 35.97 equals cubic feet.
A head of 10 feet gives a pressure of about 4-1/3 pounds to the square
inch. Let H represent the head of water in feet, and P the pressure to
the square inch. Then:
H equals P times 2.311.
P equals H times .4326.
A FIRE LUTE.
To make a fire-proof joint between the lid and body of a retort, or
crucible, use the following as a lute:
Quartz sand. 8 parts.
Clay (pure as possible) 2 parts.
Horse dung 1 part.
Mix and temper like mortar.
CONTENTS OF A VEIN.
To find the number of cubic feet per fathom of matter in a vein,
multiply its thickness in inches by 3. Great care is requisite in
estimating the ore in a vein or the amount of mineral in sight. Very
clever men often make grave mistakes in such calculations.
A MAKE-SHIFT FLUX.
Rough smelting may be done with powdered white glass, though either
borax or carbonate of soda is better. As soon as the gold is melted
and the flux fluid and still, remove the bulk of the flux with an iron
spoon, and pour the metal into a clay mould. Crush the flux for gold.
SAVING BLAST SAMPLES.
Place a quantity of spruce boughs over a hole before firing the shot,
and very few stones will fly.
A SIMPLE RETORT.
Squeeze the quicksilver amalgam containing gold through a chamois skin
or piece of cotton until it is as dry as you can get it. Then take a
large potato, cut off one end and hollow out a piece of it large
enough to receive the amalgam. Heat a shovel or a piece of sheet iron
red hot, hold the potato up and press the shovel to it, covering the
amalgam. As soon as the potato sticks fast to the shovel, turn it over
so that the potato is on the top and place it over the fire and keep
it red hot until the retorting is finished. As soon as it cools,
loosen the potato with a knife, and the gold will be underneath and
the quicksilver in the potato. The quicksilver may be recovered by
bruising the potato to pulp in a cup with water.
CLEANING AMALGAMATED PLATES.
[Illustration]
A very simple plan for getting the gold off an amalgamated copper
plate is as follows: Take out the surface dirt for the depth of nine
inches over an area a little larger than the plate to be scaled; place
six bricks around the excavation as supports for the plate. Make a
brick fire, and let it burn down to red hot embers. Lay the plate on
three iron bars resting on the bricks, and cover the face with strips
of old blanket soaked in a strong solution of borax. Keep the blankets
wet with the solution, and when the amalgam is white, remove the plate
and scrape.
CALCULATING WEIGHT OF ORE.
Measure the cubic contents of the mass; multiply this by the weight of
one cubic foot of the mineral.
For small masses, where no scales are at hand, fill a bucket with
water, and stand it in an empty barrel. Fill the bucket brimful;
introduce the rock, or ore, and measure the water it displaces. Find
the number of cubic inches in the overflow by reference to the
following table:
1 gallon equals 231 cubic inches.
1 quart equals 57.75 cubic inches.
1 pint equals 28.87 cubic inches.
1 gill equals 7.21 cubic inches.
Multiply the total so found by the specific gravity of the ore, and
the result will be the answer sought.
Supposing the bottom of the bin to be wedge-shaped, measure half the
height from the bottom to the top and multiply the number of feet by
the width and length, both in feet. This will give number of cubic
feet in the bin. Multiply the number of cubic feet by the weight of
one cubic foot of the ore, and the result will show the number of
pounds of ore the bin will hold. Divide by 2,000 to reduce to tons.
MINING REGULATIONS.
The mining regulations of every country differ, and the prospector
must learn by heart the provisions of the one he works under. A claim
notice written with a hard pencil or surveyor's marking lead on a soft
pine board will last for years.
WEIGHTS AND MEASURES.
Troy Weight.
24 grains 1 pennyweight.
20 pwts. 1 ounce.
12 ounces 1 pound.
Long Measure.
12 inches 1 foot.
3 feet 1 yard.
2 yards 1 fathom.
16-1/2 feet 1 rod.
4 rods 1 chain.
10 chains 1 furlong.
8 furlongs 1 mile.
Square Measure.
9 sq. feet 1 sq. yard.
30-1/4 sq. yds. 1 sq. rod.
40 sq. rods 1 sq. rood.
4 sq. roods 1 sq. acre.
640 sq. acres 1 sq. mile.
An acre is 209 feet square.
Land Measure.
7.92 inches 1 link.
25 links 1 rod.
4 rods 1 chain.
80 chains 1 mile.
Avoirdupois Weight.
16 drams 1 ounce.
16 ounces 1 pound.
25 pounds 1 quarter.
4 quarters 1 cwt.
20 cwt. (2,000 pounds) 1 ton.
Apothecary's Weight.
20 grains 1 scruple.
3 scruples 1 dram.
8 drams 1 ounce.
12 ounces 1 pound.
GLOSSARY.
Adamantine--Having diamond luster.
Adit--A horizontal tunnel from the surface draining a mine.
Alluvium--Deposit by streams.
Amalgamation--Combining mercury with another metal.
Analysis--A chemical search whereby the nature (qualitative) and
amount (quantitative) of the components of a substance are found out.
Aqua regia--A mixture of 3 parts hydrochloric acid with 1 part strong
nitric acid.
Arenaceous--Sandy.
Argentiferous--Silver-bearing.
Argillaceous--Clay-bearing.
Arrastra--A rotary and primitive mill.
Assay--A test.
Assay-ton--29.166 2-3 grammes.
Auriferous--Gold-bearing.
Bar--Obstruction in the bed of a river.
Bar-diggings--Claims in the shallows of streams.
Base Metals--Those not classed as precious.
Batea--Mexican gold-washing dish.
Battery--A set of stamps for crushing.
Bed--A seam or deposit.
Bed-rock--Solid stratum below porous material.
Bench--Old river bed; also called a terrace.
Booming--The sudden discharge of accumulated water.
Bort--Black diamond.
Calcite--Carbonate of lime.
Canon--Pronounced canyon; a gorge.
Carat--About 4 grains Troy.
Cement--Compacted gravel.
Color--A speck of gold.
Country Rock--The rock enclosing a vein.
Cradle--A mining apparatus; also called a rocker.
Cupriferous--Copper-bearing.
Decrepitate--Crackling when hot.
Development--Work done in opening a mine.
Dip--The inclination of a vein at right angles to its length.
Dolly--A primitive stamp-mill.
Drift--A horizontal gallery in a mine; or the rubbish left by the last
ice age.
Drifting--Driving a tunnel.
Dump--A heap of vein stuff, etc.
Exploitation--The actual mining following exploration.
Fathom--Six feet.
Fault--A break in a vein or bed.
Float-gold--Fine grains that do not sink in the water.
Float--Veinstone or ore by which a vein is traced.
Flume--Wooden troughs carrying water.
Flux--Material added to help fusion.
Foliated--In thin layers.
Gangue--Veinstone.
Gouge--A selvage of clay between vein and country rock.
Grade--The inclination of a ditch, etc.
Grating--Perforated iron sheet, or bars with spaces.
Gravel--Broken down, rounded rock fragments.
Ground Sluice--A gutter in which gold is washed.
Iridescent--Showing the hues of the rainbow.
Litharge--Proto oxide of lead.
Long Tom--A machine for saving alluvial gold.
Marl--Clay containing lime.
Miner's Inch--An arbitrary measure of water regulated by local custom.
Mundic--Iron pyrites.
Open Cut--A surface working.
Outcrop--That part of a vein showing on the surface.
Oxidation--A chemical union with oxygen.
Oxide--Combination of a metal with oxygen.
Panning--Washing gravel, or crushed rock, in a gold-miner's pan to
detect gold, etc.
Peroxide--The oxide of any substance that is richest in oxygen.
Placer--A deposit of valuable metal in gravel.
Plat--A map from an original survey.
Plumbago--Graphite or black lead.
Precipitate--Matter separated from a solution.
Pulp--Pulverized ore mixed with water.
Quarry--An open working.
Quartz--Silica.
Quartzose--Containing a large proportion of quartz.
Reduce--To turn ore into metal by taking away oxygen.
Riffle--A groove or strip to catch gold and mercury in a sluice.
Roasting--Heating in contact with air.
Shaft--A pit giving access to a vein or working.
Stratum--Bed or layer.
Striated--Marked with parallel workings.
Strip--To remove overlying material from a vein.
Sulphate--A salt containing sulphuric acid.
Sulphide--A combination of sulphur and a metal.
Sulphurets--When the miner employs this term he usually means pyrites.
Tailings--The refuse matter after ore has been crushed.
Throw--The movements of vein caused by a fault; it may be up or down.
Translucent--If light passes through a mineral, it is translucent; if
you can see the details of an object through it, it is transparent.
Underlie--The same thing as dip.
Unstratified--Without stratification or bedding.
Wash Dirt--Auriferous gravel or clay.
Whim--A machine for hoisting by a revolving drum.
Winze--An interior shaft connecting the levels.
Zinc--White oxide of zinc.
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