Produced by Dagny; John Bickers
GETTING GOLD:
A PRACTICAL TREATISE
FOR PROSPECTORS, MINERS, AND STUDENTS.
By J. C. F. Johnson, F. G. S., MEMBER OF THE AUST. INST. OF MINING
ENGINEERS;
AUTHOR OF "PRACTICAL MINING," "THE GENESIOLOGY OF GOLD," ETC.
PREPARER'S NOTE
This text was prepared from a 1898 edition, published by Charles Griffin
& Company, Limited; Exeter Street, Strand, London. It is the second
edition, revised. Numerous drawings and diagrams have been omitted.
PREFACE
Some six years ago the author published a small book entitled "Practical
Mining," designed specially for the use of those engaged in the always
fascinating, though not as invariably profitable, pursuit of "Getting
Gold." Of this ten thousand copies were sold, nearly all in Australasia,
and the work is now out of print. The London _Mining Journal_ of
September 9th, 1891, said of it: "We have seldom seen a book in which so
much interesting matter combined with useful information is given in so
small a space."
The gold-mining industry has grown considerably since 1891, and it
appeared to the writer that the present would be a propitious time to
bring out a similar work, but with a considerably enlarged scope. What
has been aimed at is to make "Getting Gold" a compendium, in specially
concrete form, of useful information respecting the processes of winning
from the soil and the after-treatment of gold and gold ores,
including some original practical discoveries by the author. Practical
information, original and selected, is given to mining company
directors, mine managers, quartz mill operators, and prospectors. In
"Rules of Thumb," chapters XI. and XII., will be found a large number
of useful hints on subjects directly and indirectly connected with
gold-mining.
The author's mining experience extends back thirty years and he
therefore ventures to believe with some degree of confidence that the
information, original or compiled, which the book contains, will be
found both useful and profitable to those who are in any capacity
interested in the gold-mining industry.
J. C. F. J.
LONDON, November, 1896.
GETTING GOLD
CHAPTER I
INTRODUCTORY
GOLD is a name to charm by. It is desired by all nations, and is the one
metal the supply of which never exceeds the demand. Some one has aptly
said, "Gold is the most potent substance on the surface of our planet."
Tom Hood sings:
Gold, gold, gold, gold!
Bright and yellow, hard and cold;
Molten, graven, hammered, rolled,
Heavy to get, and light to hold;
Stolen, borrowed, squandered, doled.
That this much appreciated metal is heavy to get is proved by the high
value which has been placed on it from times remote to date, and that it
is light to hold most of us know to our cost.
We read no farther than the second chapter in the Bible when we find
mention of gold. There Moses speaks of "the land of Havilah, where there
is gold"; and in Genesis, chapter xxiv., we read that Abraham's servant
gave Rebekah an earring of half a shekel weight, say 5 dwt. 13 grs.,
and "two bracelets of ten shekels weight," or about 4 1/2 ozs. Then
throughout the Scriptures, and, indeed, in all historic writings, we
find frequent mention of the king of metals, and always it is spoken of
as a commodity highly prized.
I have sometimes thought, however, that either we are mistaken in the
weights used by the Hebrew nation in early days, or that the arithmetic
of those times was not quite "according to Cocker." We read, I. Kings x.
and xli., that Solomon in one year received no less than six hundred
and three score and six talents of gold. If a talent of gold was, as has
been assumed, 3000 shekels of 219 grains each, the value of the golden
treasure accumulated in this one year by the Hebrew king would have been
3,646,350 pounds sterling. Considering that the only means of "getting
gold" in those days was a most primitive mode of washing it from river
sands, or a still more difficult and laborious process of breaking the
quartz from the lode without proper tools or explosives, and then slowly
grinding it by hand labour between two stones, the amount mentioned is
truly enormous.
Of this treasure the Queen of Sheba, who came to visit the Hebrew
monarch, contributed a hundred and twenty talents, or, say, 600,000
pounds worth. Where the Land of Ophir, whence this golden lady came, was
really situated has evoked much controversy, but there is now a general
opinion that Ophir was on the east coast of Africa, somewhere near
Delagoa Bay, in the neighbourhood of the Limpopo and Sabia rivers. It
should be mentioned that the name of the "black but comely" queen was
Sabia, which may or may not be a coincidence, but it is certainly true
that the rivers of this district have produced gold from prehistoric
times till now.
The discovery of remarkable ruins in the newly acquired province of
Mashonaland, which evince a high state of civilisation in the builders,
may throw some light on this interesting subject.
The principal value of gold is as a medium of exchange, and its high
appreciation is due, first, to the fact that it is in almost universal
request; and, secondly, to its comparative scarcity; yet, oddly enough,
with the exception of that humble but serviceable metal iron, gold is
the most widely distributed metal known. Few, if any, countries do not
possess it, and in most parts of the world, civilised and uncivilised,
it is mined for and brought to market. The torrid, temperate, and frigid
zones are almost equally auriferous. Siberia, mid-Asia, most parts of
Europe, down to equatorial and southern Africa in the Old World, and
north, central, and southern America, with Australasia, in what may be
termed the New World, are all producers of gold in payable quantities.
In the earlier ages, the principal source of the precious metal was
probably Africa, which has always been prolific in gold. To this day
there are to be seen in the southern provinces of Egypt excavations and
the remains of old mine buildings and appliances left by the ancient
gold-miners, who were mostly State prisoners. Some of these mines were
worked by the Pharaohs of, and before, the time of Moses; and in these
dreadful places thousands of Israelites were driven to death by the
taskmaster's whip. Amongst the old appliances is one which approximated
very closely to the amalgamating, or blanket table, of a modern quartz
mill.
The grinding was done between two stones, and possibly by means of such
primitive mechanism as is used to-day by the natives of Korea.
The Korean Mill is simply a large hard stone to which a rocking motion
is given by manual power by means of the bamboo handles while the ore is
crushed between the upper and basement stone.
Solomon says "there is no new thing under the sun"; certainly there is
much that is not absolutely new in appliances for gold extraction. I
lately learned that the principle of one of our newest concentrating
machines, the Frue vanner, was known in India and the East centuries
ago; and we have it on good authority--that of Pliny--that gold saving
by amalgamation with mercury was practised before the Christian era.
It will not be surprising then if, ere long, some one claims to have
invented the Korean Mill, with improvements.
Few subjects in mineralogical science have evoked more controversy than
the origin of gold. In the Middle Ages, and, indeed, down to the time
of that great philosopher, Sir Isaac Newton, who was himself bitten
with the craze, it was widely believed that, by what was known as
transmutation, the baser metals might be changed to gold; and much time
and trouble were expended in attempts to make gold--needless to say
without the desired result. Doubtless, however, many valuable additions
to chemical science, and also some useful metallic alloys, were thus
discovered.
The latest startling statement on this subject comes from, of course,
the wonderland of the world, America. In a recently published journal it
is said that a scientific metallurgist there has succeeded in producing
absolutely pure gold, which stands all tests, from silver. Needless
to say, if this were true, at all events the much vexed hi-metallic
question would be solved at once and for all time.
It is now admitted by all specialists that the royal metal, though
differing in material respects in its mode of occurrence from its
useful but more plebeian brethren of the mineral kingdom, has yet been
deposited under similar conditions from mineral salts held in solution.
The first mode of obtaining this much desired metal was doubtless by
washing the sand of rivers which flowed through auriferous strata. Some
of these, such as the Lydian stream, Pactolus, were supposed to renew
their golden stores miraculously each year. What really happened was
that the winter floods detached portions of auriferous drift from the
banks, which, being disintegrated by the rush and flow of the water,
would naturally deposit in the still reaches and eddies any gold that
might be contained therein.
The mode of washing was exactly that carried on by the natives in
some districts of Africa to-day. A wooden bowl was partly filled with
auriferous sand and mud, and, standing knee-deep in the stream, the
operator added a little water, and caused the contents of the bowl to
take a circular motion, somewhat as the modern digger does with his tin
dish, with this difference, that his ancient prototype allowed the water
and lighter particles to escape over the rim as he swirled the stuff
round and round. I presume, in finishing the operation, he collected
the golden grains by gently lapping the water over the reduced material,
much as we do now.
I have already spoken of the mode in which auriferous lode-stuff was
treated in early times--i.e., by grinding between stones. This is also
practised in Africa to-day, and we have seen that the Koreans, with
Mongolian acuteness, have gone a step farther, and pulverise the quartz
by rocking one stone on another. In South America the arrastra is still
used, which is simply the application of horse or mule power to the
stone-grinding process, with use of mercury.
The principal sources of the gold supply of the modern world have
been, first, South America, Transylvania in Europe, Siberia in Asia,
California in North America, and Australia. Africa has always produced
gold from time immemorial.
The later development in the Johannesburg district, Transvaal, which has
absorbed during the last few years so many millions of English capital,
is now, after much difficulty and disappointment--thanks to British
pluck and skill--producing splendidly. The yield for 1896 was 2,281,874
ounces--a yield never before equalled by lode-mining from one field.
In the year 1847 gold was discovered in California, at Sutor's sawmill,
Sacramento Valley, where, on the water being cut off, yellow specks and
small nuggets were found in the tail race. The enormous "rush" which
followed is a matter of history and the subject of many romances, though
the truth has, in this instance, been stranger than fiction.
The yield of the precious metal in California since that date up to 1888
amounts to 256,000,000 pounds.
Following close on the American discovery came that of Australia, the
credit of which has usually been accorded to Hargraves, a returned
Californian digger, who washed out payable gold at Lewis Ponds Creek,
near Bathurst, in 1851. But there is now no reason to doubt that gold
had previously been discovered in several parts of that great island
continent. It may be news to many that the first gold mine worked in
Australia was opened about twelve miles from Adelaide city, S.A., in the
year 1848. This mine was called the Victoria; several of the Company's
scrip are preserved in the Public Library; but some two years
previous to this a man named Edward Proven had found gold in the same
neighbourhood.
Most Governments nowadays encourage in every possible way the discovery
of gold-fields, and rewards ranging from hundreds to thousands of pounds
are given to successful prospectors of new auriferous districts. The
reward the New South Wales authorities meted out to a wretched convict,
who early in this century had dared to find gold, was a hundred lashes
vigorously laid on to his already excoriated back. The man then very
naturally admitted that the alleged discovery was a fraud, and that
the nugget produced was a melted down brass candlestick. One would have
imagined that even in those unenlightened days it would not have been
difficult to have found a scientist sufficiently well informed to put a
little nitric acid on the supposed nugget, and so determine whether it
was the genuine article, without skinning a live man first to ascertain.
My belief is that the unfortunate fellow really found gold, but, as Mr.
Deas Thompson, the then Colonial Secretary, afterwards told Hargraves in
discouraging his reported discovery, "You must remember that as soon
as Australia becomes known as a gold-producing country it is utterly
spoiled as a receptacle for convicts."
This, then, was the secret of the unwillingness of the authorities to
encourage the search for gold, and it is after all due to the fact
that the search was ultimately successful beyond all precedent,
that Australia has been for so many years relieved of the curse of
convictism, and has ceased once and for all to be a depot for the
scoundrelism of Britain--"Hurrah for the bright red gold!"
Since the year 1851 to date the value of the gold raised in the
Australasian colonies has realised the enormous amount of nearly
550,000,000 pounds. One cannot help wondering where it all goes.
Mulhall gives the existing money of the world at 2437 million pounds,
of which 846 millions are paper, 801 millions silver, and 790 millions
gold. From 1830 to 1880 the world consumed by melting down plate, etc.,
4230 tons of silver more than it mined. From 1800 to 1870 the value of
gold was about 15 1/2 times that of silver. From 1870 to 1880 it was 167
times the value of silver and now exceeds it over twenty times. In 1700
the world had 301 million pounds of money; in 1800, 568 million pounds;
and in 1860, 1180 million pounds sterling.
The gold first worked for in Australia, as in other places, was of
course alluvial, by which is usually understood loose gold in nuggets,
specks, and dust, lying in drifts which were once the beds of long
extinct streams and rivers, or possibly the moraines of glaciers, as in
New Zealand.
Further on the differences will be mentioned between "alluvial" and
"reef" or lode gold, for that there is a difference in origin in many
occurrences, is, I think, provable. I hold, and hold strongly, that true
alluvial gold is not always derived from the disintegration of lodes or
reefs. For instance, the "Welcome Nugget" certainly never came from a
reef. No such mass of gold, or anything approaching it, has ever yet
been taken from a quartz matrix. It was found at Bakery Hill, Ballarat,
in 1858, weight 2195 ozs., and sold for 10,500 pounds. This was above
its actual value.
The "Welcome Stranger," a still larger mass of gold, was found amongst
the roots of a tree at Dunolly, Victoria, in 1869, by two starved out
"fossickers" named Deeson and Oates. The weight of this, the largest
authenticated nugget ever found was 2268 1/2 ozs., and it was sold for
10,000 pounds, but it was rendered useless as a specimen by the finders,
who spent a night burning it to remove the adhering quartz.
But the ordinary digger neither hopes nor expects to unearth such
treasures as these. He is content to gather together by means of
puddling machine, cradle, long tom, or even puddling tub and tin dish,
the scales, specks, dust, and occasional small nuggets ordinarily met
with in alluvial "washes."
Having sunk to the "wash," or "drift," the digger, by means of one or
more of the appliances mentioned above, proceeds to separate the gold
from the clay and gravel in which it is found. Of course in large
alluvial claims, where capital is employed, such appliances are
superseded by steam puddles, buddles, and other machinery, and sometimes
mercury is used to amalgamate the gold when very fine. Hydraulicing is
the cheapest form of alluvial mining, but can only be profitably carried
out where extensive drifts, which can be worked as quarry faces, and
unlimited water exist in the same neighbourhood. When such conditions
obtain a few grains of gold to the yard or ton will pay handsomely.
Lode or reef mining, is a more expensive and complicated process,
requiring much skill and capital. First, let me explain what a lode
really is. The American term is "ledge," and it is not inappropriate or
inexpressive. Imagine then a ledge, or kerbstone, continuing to unknown
depths in the earth at any angle varying from perpendicular to nearly
horizontal. This kerbstone is totally distinct from the rocks which
enclose it; those on one side may be slate, on the other, sandstone; but
the lode, separated usually by a small band of soft material known
to miners as "casing," or "fluccan," preserves always an independent
existence, and in many instances is practically bottomless so far as
human exploration is concerned.
There are, however, reefs or lodes which are not persistent in depth.
Sometimes the lode formation is found only in the upper and newer
strata, and cuts out when, say, the basic rocks (such as granite, etc.)
are reached. Again, there is a form of lode known among miners as a
"gash" vein. It is sometimes met with in the older crystalline slates,
particularly when the lode runs conformably with the cleavage of the
rock.
Much ignorance is displayed on the subject of lode formation and the
deposition of metals therein, even by mining men of long experience.
Many still insist that lodes, particularly those containing gold, are of
igneous origin, and point to the black and brown ferro-manganic outcrops
in confirmation. It must be admitted that often the upper portions of
a lode present a strong appearance of fire agency, but exactly the same
appearance can be caused by oxidation of iron and manganese in water.
It may now be accepted as a proven fact that no true lode has been
formed, or its metals deposited except by aqueous action. That is to
say, the bulk of the lode and all its metalliferous contents were once
held in solution in subterranean waters, which were ejected by geysers
or simply filtered into fissures formed either by the shrinkage of the
earth's crust in process of cooling or by volcanic force.
It is not contended that the effect of the internal fires had no
influence on the formation of metalliferous veins, indeed, it is certain
that they had, but the action was what is termed hydrothermal (hot
water); and such action we may see in progress to-day in New Zealand,
where hot springs stream or spout above the surface, when the silica
and lime impregnated water, reduced in heat and released from pressure,
begins forthwith to deposit the minerals previously held in solution.
Hence the formation of the wondrous Pink and White Terrace, destroyed
by volcanic action some eight years since, which grew almost while
you watched; so rapidly was the silica deposited that a dead beetle or
ti-tree twig left in the translucent blue water for a few days became
completely coated and petrified.
Gold differs in its mode of occurrence from other metals in many
respects; but there is no doubt that it was once held in aqueous
solution and deposited in its metallic form by electro-chemical action.
It is true we do not find oxides, carbonates, or bromides of gold in
Nature, nor can we feel quite sure that gold now exists naturally as a
sulphide, chloride, or silicate, though the presumption is strongly
that it does. If so, the deposition of the gold may be ceaselessly
progressing.
Generally reef gold is finer as to size of the particles, and, as a
rule, inferior in quality to alluvial. Thus, in addition to the extra
labor entailed in breaking into one of the hardest of rocks, quartz,
the _madre de oro_ ("mother of gold") of the Spaniards, there is the
additional labour required to pulverise the rock so as to set free the
tiniest particles of the noble metal it so jealously guards. There is
also the additional difficult operation of saving and gathering together
these small specks, and so producing the massive cakes and bars of gold
in their marketable state.
Having found payable gold in quartz on the surface, the would-be miner
has next to ascertain two things. First, the strike or course of the
lode; and secondly, its underlie, or dip. The strike, or course, is the
direction which the lode takes lengthwise.
In Australia the term "underlie" is used to designate the angle from
the perpendicular at which the lode lies in its enclosing rocks, and by
"dip" the angle at which it dips or inclines lengthwise on its course.
Thus, at one point the cap of a lode may appear on the surface, and some
distance further the cap may be hundreds of feet below. Usually a shaft
is sunk in the reef to prove the underlie, and a level, or levels,
driven on the course to ascertain its direction underground, also if
the gold extends, and if so, how far. This being proved, next a vertical
shaft is sunk on the hanging or upper wall side, and the reef is either
tapped thereby, or a cross-cut driven to intersect it.
We will now assume that our miners have found their lode payable, and
have some hundreds of tons of good gold-bearing stone in sight or at the
surface. They must next provide a reducing plant. Of means for crushing
or triturating quartz there is no lack, and every year gives us fresh
inventions for the purpose, each one better than that which preceded
it, according to its inventor. Most practical men, however, prefer to
continue the use of the stamper battery, which is virtually a pestle
and mortar on a large scale. Why we adhere to this form of pulverising
machine is that, though somewhat wasteful of power, it is easily
understood, its wearing parts are cheaply and expeditiously replaced,
and it is so strong that even the most perversely stupid workman cannot
easily break it or put it out of order.
The stone, being pounded into sand of such degree of fineness as
the gold requires, passes through a perforated iron plate called a
"grating," or "screen," on to an inclined surface of copper plates faced
with mercury, having small troughs, or "riffles," containing mercury,
placed at certain distances apart.
The crushed quartz is carried over these copper "tables," as they are
termed, thence over the blanket tables--that is, inclined planes covered
with coarse serge, blankets, or other flocculent material--so that the
heavy particles may be caught in the hairs, or is passed over vanners or
concentrating machines. The resulting "concentrates" are washed off from
time to time and reserved for secondary treatment.
To begin with, they are roasted to get rid of the sulphur, arsenic,
etc., which would interfere with the amalgamation or lixiviation, and
then either ground to impalpable fineness in one of the many triturating
pans with mercury, or treated by chlorine or potassium cyanide.
If, however, we are merely amalgamating, then at stated periods the
battery and pans are cleaned out, the amalgam rubbed or scraped from
the copper plates and raised from the troughs and riffles. It is then
squeezed through chamois leather, or good calico will do as well, and
retorted in a large iron retort, the nozzle of which is kept in water so
as to convert the mercury vapour again to the metallic form. The result
is a spongy cake of gold, which is either sold as "retorted" gold or
smelted into bars.
The other and more scientific methods of extracting the precious metal
from its matrices, such as lixiviation or leaching, by means of solvents
(chlorine, cyanogen, hyposulphite of soda, etc.), will be more fully
described later on.