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'Gold' its properties, modes of extraction, value, &c., &c Claudet, F. G. (Francis George), 1837-1906 1871

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Although this is a gold producing country, and the
precious metal passes through the hands of so many,
there is, doubtless, a large number of persons quite uninformed with respect to the conditions under which
gold occurs in nature, the various processes by which it
is obtained, and its commercial value after it has been
This little pamphlet has been written with the view of
presenting the subject to the Public in as condensed a
form as possible, in order to enable tho*e who cannot
spare the time, or who may not have the patience, to
read through a large work, to acquire, by the perusal of
a few pages, an insight into some of the most important
features 01 an interesting and useful Branch of Study.  History and Properties of Gold.
Gold has been known from the earliest ages of the
world, and has been universally employed as a medium
of exchange.
We hear of its having been used by the Hebrews,
Egyptians, Greeks, Romans and other ancient nations, in
about the same manner as it is at the present day. Tfae
first allusion made to gold in the Bible occurs in the 2nd
chapter of Genesis, v. Hand 12. But the earliest practical application of the use of gold appears to be that
mentioned in the 24th chapter of Genesis, v. 22, B. C ,
185*7, where it is evident that the precious metal was
not only known but wrought. Eleazer, the servant of
Abraham, gave to Rebecca, the future wife of Isaac, an
earring and two bracelets of gold. It is also mentioned by Moses in the 31st chapter of Numbers,
where he says, "Only the gold and the silver, the brass,
the iron, the tin, and the lead, everything that may
abide the fire, ye shall make it pass through the fire and
it shall be clean." The alchymists designated it by the
name, and gave it the symbol of Sol.
It is the most precious of all the metals, possesses a beau"
tifully rich yellow color, and has no perceptible taste or
smell. When pure its specific gravity is 19.3, being,
with the exception of Platinum and Iridiam, the heaviest
of ail known substances. In its native state the specific
grayity yaries from 13 to 18.
It is pre-eminently ductile aud malleable; so malleahU
tnnt it may be beaten out into leaves so thin that one
grain of gold will cover 57 square inches; so ductile that
a single grain weight may be drawn into a wire 500 foe.t
It fuses at a temperature estimated at about 2020
degs. Fahrenheit.
Gold is invariably found in the metallic state, but is
never quite pure, being alloyed with silver in different
proportions, and being generally associated with small
quiiitities of copper, iron and other metals.-
There are other combinations of gold, which are, however, of comparatively small commercial importance.
One, an alloy of gold with Palladium, called Palladium
gold, another with Rhodium, called Rhodium gold.
There is also a native amalgam of gold and mercury.
The Plectrum of Pliny, so called by him on account of
its amber color, seems to be a definite compound;
specimens from Siberia, analyzed by Klaproth, were
found to contain 64 parts of gold and 36 parts of silver.
There are few parts of the globe in which gold has
not been found more or less to exist, but it occurs very
irregularly, here and there in great abundance, in some
places in minute quantity. Prior to the great Califor-
nian discovery, in 1847, various countries in Europe,
Asia, Africa and America had contributed large supplies
of the precious metal, the most celebrated mines of
which, in Europe, are those in Transylvania, which have
been worked since the time of the Romans.
There are mines in various parts of Africa: those on
the Mozambique Coast are supposed by some historians
to have been the famous Ophir of the time of Solomon.
Subsequent to the discoveries in California and Australia
the old gold mines have become of comparative insig- HISTORY AND PROPERTIES OF GOLD. 7
nificance, as these two regions now produce more than
four times the amount yielded by all the other countries
put together.
Further discoveries of considerable importance continue to be made, among which those in British Columbia
occupy a prominent position.
Gold is largely obtained from alluvial washings, in the
shape of fine particles and water-worn plates and scales*
but crystallized specimens are occasionally met with.
These crystals are in forms belonging to the monometric
system, such as cubes and octahedrons, generally the
latter. Sometimes larger lumps, or "nuggets," are found,
weighing several ounces, and in a few rare instances,
many pounds.
Geological Position of Gold.
There are four different lithological situations in which
gold occurs :—
1. In veins, generally enclosed in metamorphic slates.
2. In small threads, traversing the quartzose veins of
the more highly crystalline rocks.
3. In placer deposits formed by ancient river-systems,
known as "deep diggings."
.4. In placer deposits, distributed by the present river-
system, giving rise to what are called " shallow diggings."
The most productive gold-bearing quartz is generally
found to be that which intersects talcose, chloritic and
argillaceous schists, although valuable gold veins are
occasionally met with in granite, gneiss and porphyry.
These veins have most frequently the same | dip" and
"strike" as the slaty rocks in which they are enclosed.
Their width varies from a fraction of an inch to several
feet, some have been known to attain the extraordinary
thickness of a hundred feet; and their richness in gold
is equally uncertain.
When rocks remain stratified, in nearly the same position in which they were originally deposited, they are
rarely found to be highly auriferous; but when they have
been upheaved, or raised on edge, by eruptive masses,
and have assumed a crystalline texture, there is good
reason to expect the presence of the precious metal.
The auriferous veins are presumed, by some geologists,
to have originated at the time of the met amorphic action,
by which the change in the strata was effected. This
action does not, however, appear to have been confined
to any particular geological epoch, and -it is probable
that these alterations, which are most likely very slow in
their progress, may have been repeated at periods of
time exceedingly distant from each other.
The widest veins are not usually the richest, and it has
been found that some of the laminoe running parallel
with the enclosing walls are uniformly more productive
than others. It therefore not unfrequently happens that
a portion of a vein, rich enough to be treated with advantage, is separated from another band, comparatively
worthless, by a distinct heading, or false wall.
As a general rule those veins are most productive
which afford considerable quantities of sulphides; although, near the surface, these have, almost invariably,
become decomposed, thereby liberating the enclosed
granular gold, and staining the quartz of a brown or
reddish color.
When gold is found in white quartz, without sulphides,
it is in most instances in flakes and granules of consider-
able size, and is consequently visible to the naked eye;
but such veins, although affording fine specimens, are
not often regnlarly and remuneratively productive. GEOLOGICAL POSITION OF GOLD. 9
The most profitable veins are generally only of moderate size, and seldom exhibit visible gold.
It was formerly believed that veins of auriferous
quartz become gradually less productive as greater,
depths from the surface are attained, but experience has
shown that this is in reality not the case. It is true
that gold mines have fluctuated considerably in their
richness at different depths, but it has not been found
that these variations correspond with a gradual impoverishment in the deeper levels.
An illustration of this fact is found in many veins ia
The North Star vein is now worked on its inclination
to a depth of 750 feet, and affords quartz yielding, on an
average, gold of the value of $35 per ton of 2000 fi>s.f
whereas in the upper levels the value did not exceed $20
per ton.
Hayward's mine, in Amador County, is another still
more striking instance of the produce of a vein not decreasing as it goes down. This ledge has been worked
on its inclination to a depth of over 1250 feet, and yields
quartz of much greater value than that obtained from
the same vein nearer the surface.
The yield of the quartz veins of Victoria has also not
been found to decrease in depth. Some mines have been
worked 500 feet from the surface and have experienced
no diminution in their produce.
The greater portion of the gold of commerce, however, is derived from "gold-washings," or the separation
of the metal from the superficial detritus, which is included by Geologists among the drift and alluvial deposits..
The process by which these auriferous deposits have
been formed is a question which has not yet been satisfactorily solved. 10
The prevailing opinion is that, by various operations
of nature, the gold has been breken away from the rock
or vein in which it was elaborated, and has been carried
by water some distance and then deposited along with
the fragments of the rocks and minerals with which it
was associated.
Professor Whitney says: " The separation of the gold
from its original matrix and its deposition among the
strata of gravel, sand and clay, or beneath them upon
the surface of the rock, has been the result of causes
acting through an immense period of time; and which
have not yet ceased to operate, although their energy
seems no longer equal to what it must have been at a
former epoch. The rocky strata jf the earth are constantly undergoing abrasion from the combined action of
various meteorological causes; of which one of the most
powerful at present is the alternate freezing and thawing
of water in fissures and cavities, which tends to wear
away and disintegrate the most elevated portions,
especially of the slaty beds, and to carry down the
abraded and loosened materials, and spread them out in
the adjacent valleys. In lofty and rugged mountain
chains, where torrents of rain frequently fall, and the
streams', suddenly swollen to a great volume, rush with
tremendous violence down rapidly declining valleys, their
force becomes capable of wearing away the rocks with
great rapidity."
"This mechanical action is frequently aided by a
chemical one; the strata undergoing a molecular change
which softens them and renders their abrasion easy.
As the enclosing rocks are thus worn away, the quartz-
veins become disaggregated by the oxidation of the iron
they contain, and are themselves crashed into fragments
and borne down into the valleys, where the metallic par- GEOLOGICAL POSITION OF GOLD. 11
tides, having by far the highest specific gravity, are
first deposited and sink to the bottom, while the lighter
earthy portions are carried farther."
Sir Roderick Murchison asserts that the more or less
superficial deposits which contain gold, and known as
" deep diggings," are not to be confounded with detritus
formed by present atmospheric action, but rather that
they are the result of diluvial currents connected with,
and originating in, physical changes in the earth's surface, such as the elevation of mountain chains.
Another explanation of the formation of deep diggings
has been advanced by Davison, which is perhaps entitled
to a certain amount of consideration, although the great
majority of Geologists incline to the opinions of Sir
Roderick Murchison and Professor Whitney.
Davison asserts that placer gold has been distributed
and deposited by means of some igneous liquid rock, or
lava, and that, quartz-veins and dykes have been the
fissures of discharge.
His reasons for this conclusion are, that alluvial gold
often has a fused appearance, and has a ragged and irregular surface, which must have been destroyed by
abrasion; that it is found upon "bedrocks" in such
shape and position that the agency of water alone could
not have so placed it, and that it also occurs richly deposited in the neighborhood of ancient volcanic disturbance.
However much Geologists may differ with regard to
the origin of " deep diggings," there can be no doubt
that the distribution of gold by the present river-system,
constituting the " shallow diggings" is purely referable
to the natural grinding away of auriferous rocks, and the
deposition of the gold by the agency of water. Extraction of Gold.
Gold mines may be divided into two distinct classes,
viz: placer mines, in which the metal is found embedded
in clay, sand, or gravel; and quartz or vein mines, in
which it is met with in its original matrix.
In the former, the gold producing material is called
"pay-dirtj" which on being subjected to the action of
water, becomes disintegrated, and the lighter portion s=
are mechanically carried off, whilst the gold, being
heavier, remains behind.-
In the latter, the rock has to be first obtained by the
ordinary mining operations, as practiced with regard to
other metals, then reduced to powder by mechanical
means, and finally the gold is collected, either by washing or amalgamation.
Placer mines are generally those which first attract
attention in a new country, and from which profitable
returns are most easily obtained.
Water is the great agent by which placer mining is
carried on.
These mines are of two classes, the shallow and the
deep f the former are generally found in the beds of
ravines, on the bars and in the beds of modern rivers,
and on shallow.flats.
In the latter, the pay dirt is often found at great
depths from the surface, and is frequently covered by
thick beds of lava, or volcanic- ash, as in the case of the
deposits under Table Mountain, Tuolumne County, and
• near Nevada City, California. *
In the deeper placers, the gold drifts are reached
either by shafts, or by means of tunnels. The pay dirt
is thus extracted, conveyed to the surface and subjected
to the process of washing.
In other instances, hydraulic mining is resorted to.
Jets of water, under a great presure, obtained from a
high column, are directed against the deposits of sand
and gravel, which are thus disintegrated and carried
away by the current.
This is the most economical and expeditious method
of working placer mines, when a sufficient supply and/
pressure of water can be obtained, and there is enough
declivity below the auriferous beds to allow of the detritus being readily disposed of.
The pay dirt is almost invariably covered by layers of
barren clay and sand, which are, in the shallow diggings,
removed by the use of the pick and shovel; but in
hydraulic workings, the whole is washed away by the
force of a stream of water playing against it, and any
particles of gold which it may contain are caught in the
sluices through which the lighter materials pass.
According to their topographieal position, placer
mines, besides being classed as shallow and deep, are
subdivided into hill, bench, flat, bar, gulch and river
Hill diggings are in the sides of hills; bench diggings
are on narrow benches on the' declivities of hills, and
above the level of existing rivers; flat diggings are
those on flats or small plains; bar diggings are usually
in sand and gravel, on the sides of streams, and, ordinarily, above the surface of the water; gulch diggings
are found in ravines and gullies, through which water
passes only in times of excessive floods; river diggings
are those which exist in the beds of rivers. 14
The terms sluice, hydraulic, tunnel, dry diggings, &c,
are used to describe the different means employed for
reaching the auriferous deposits, and separating and collecting the gold.
The most simple appliance for the separation of gold
is the well-known pan, which is used either for washing
or as a receptacle for gold, amalgam, &c. After a certain amount of practice the miner is able to get rid of
the whole of the sand, clay and stones, retaining in the
angle of the pan the geld and a small quantity of black
sand, which is too heavy to be separated from the gold
by washing. It can, however, after drying, be, to a great
extent, removed by the process of blowing and the use
of the magnet.
The cradle consists of a box usually about forty inches
in length and twenty in width, with one end from fiiteen
to twenty inches in height, the sides being sloped off at
the lower extremity like those of a coal-scuttle, the
.whole standing on rockers.
At the upper end of the cradle is the hopper, or
riddle box, twenty inches square and six in depth, of
which the bottom is composed of sheet iron, perforated
with holes half an inch in diameter. This is not' fastened
to the cradle, but can be lifted on and off at pleasure
and fits in so as to be quite steady when in its right position.
Beneath the riddle is an apron, made by stretching a
piece of canvass on a' framework resting on fillets,
inclined from the bottom edge of the riddle towards the
head of the cradle. Across the bottom are two riffle
bars, about three-quarters of an inch in height, one
towards the middle,' and the other at the lower end.
The dirt is shovelled into the hopper, and the miner
rocks the cradle with one hand, whilst with the other he EXTRACTION OF GOLD.
pours water upon the dirt. The action of the water and
motion together disintegrates the dirt, which, passes
through the riddle and falls upon the apron, finally,
escaping at the lower end, leaving the gold, black sand
and heavier particles of gravel behind the riffle bars.
Mercury is sometimes used in the rocker but is not
generally recommended.
But by far the most important arrangement is the
sluice, which is now almost uuiversally employed for the
collection of gold from placer mines.
The sluice is a long wooden trough, having a considerable inclination, into which the pay dirt is shovelled,
and through which a rapid stream of water is continually flowing. At the bottom of this trough is a series
of riffles, generally containing quicksilver, by which the
gold is retained, whilst the clay, sand and gravel are
carried off by the force of the current.
The ordinary sluice is composed of a series of rough
wooden boxes, each twelve feet in length, and from sixteen to twenty inches in width, and from ten inches to a
foot in depth.
The descent of a.sluice is called its "grade," and is
commonly from ten to eighteen inches on each box of
twelve feet in length. This " grade " is regulated by the
position and length of the apparatus and the nature of
the dirt to be washed.
It is important to guard against giving too great an
inclination, as there would be danger of losing the fine
particles of gold; while, when clay is present in quantity,
a small inclination will not easily effect its disintegration. A good deal of practice and judgment is obviously
necessary to ensure the smallest loss of gold.
As a general rule, however, a fall of less than ten
inches, or more than twenty inches, on the length of a 16 EXTRACTION. OF GOLD,
twelve-foot box, is not suitable for the ordinary sluice.
If the pay dirt contain large blocks of stone and boulders, a large body of water aDd a rapid current are
required. The upper part of a sluice is sometimes made
steep in order to effect the disintegration of the dirt,
whilst the lower is placed at a less inclination for the
purpose of collecting the gold, and this arrangement is
often found advantageous.
When the clay is very tenacious and rolls into balls,
the lumps should be broken up at the head of the sluice,
as balls of plastic clay, passing through the boxes, not
only retain any particles of gold they may contain, but
are also liable to pick up others over which they may
pass in their course.
Sluice boxes are provided with a false bottom for the
purpose of retaining the gold, which would otherwise
not only be taken away by the force of the current, but
the bottoms themselves be rapidly worn out by the
attrition of the stones and gravel passing over them.
Generally these false bottoms consist of longitudinal
bars, from two to four inches in thickness, from three to
seven inches in width, and about five feet and a half in
length. They are wedged in the boxes, an inch or two
apart, by cross pieces, so that two lengths of bars are
fitted in the bottom of each box.
In the depressions thus formed, the gold, mercury,
and amalgam are eaught. When the sluice boxes have
been all joined together, and the bars wedged into the
bottom of each, the apparatus is ready for working, and
the pay dirt is shoveled in at the head.
Abcut an hour or two after the commencement of
sluicing, some quicksilver is poured into the head of the
apparatus, whence it gradually finds its way downwards.
The greater the amount of fine gold present, the larger r
must be the quantity of mercury used. Small quamiti*»
of quicksilver are also sometimes introduced between
the bars and various other places in the boxes.
When the gold is exceedingly fine an amalgamated copper plate is sometimes resorted to. This .plate is about
three feet by six, Is set nearly level, and, when the slnice
la very large, the stream is frequently divided into two or
three separate portions, each of which is conducted over
a distinct amalgamated plate. A well amalgamated copper plate is considered as effective for saving fine gold,
as an equal surface of pure mercury, and is not only
cheaper, but also more easily managed.
The amalgamation is effected by washing the plate
with dilute nitric acid, and then rubbing on, with a rag,,
quicksilver, on which a little diluted nitric acid has been
first poured. When a plate has been once well covered,
this operation need never be repeated, it being only
necessary to sprinkle its surface occasionally with a little,
Jresh quicksilver, in proportion as the gold caught con-,
verts it into a solid amalgam. In order that these plates
should work well, the current should be slow, and tidewater shallow, otherwise a considerable portion of the
fine gold -might escape without coming in contact with
the face of the plate.
The collection of the dirt which accumulates in the bottom of the sluice, and the separation from it of,
amalgam, and quicksilver, is called the "eleaning-up,"
And the time between one cleaning-up and another is
called a "run." A run commonly lasts about a week,
and the cleaniog-up is not unfrcquwntly reserved for
the Sunday.   This occupies about half a day.
The amalgam and mercury take \ from, the siuxe arc
first separated from any sand, &c, by panning., then
itrained through buckskin, or close canvas, which allow* EXTRACTION OF GOLD.
the quicksilver to pass through, but retains the amalgam.
To obtain the gold, the amalgam is heated to volatilize
the quicksilver; the gold is left in the form of a porous
mass of a light yellow color.
*This operation is most economically performed in a
cast iron retort, provided with a refrigerator, by which
the mercury is condensed and can be collected for subsequent use. But the miners often drive off the quicksilver by simply heating the amalgam in a shovel.
In small sluices, the bars are sometimes placed in a
series of zigzags, instead of longitudinally or transversely.
'The "under-current sluice" is a modification which is
often found advantageous.
A grating is placed in the bottom of the lower extremity of the last box in the series, and beneath this is
introduced another sluice with a lower grade and fresh
srupply of water.
The impetus acquired by the large boulders, in the
first sluice, causes them to roll off over the grating, and,
together with a portion of the water, to escape at the
lower end; whilst the introduction of clear water, the
less inclination, and more moderate current, arrest many
pxrticles of gold that would, under ordinary circumstances, be lost.
There are also "rock sluices," but they are more
difficult to clean up.
In "tail sluices" stone bottoms are used, having an
inclination of about an inch to the foot. To clean up it
is necessary to remove the stones. Tail are use'd
for collecting gold still retained by the dirt which has
passed through the ordinary sluice. They are only
cleaned up at ihe end of several weeks, and only require
attention sufficient to prevent their choking. They are
generally large, long, and paved with blocks of Stone, or EXTRACTION OF GOLD. 19
wood placed on end, and often afford large profits to
their proprietors.
"Ground sluices " are used in localities where there is
a large supply of water, plenty of pay dirt of low produce, and the necessary declivity.
A small gutter is first made with a certain inclination,
and into this is directed a stream of water, by the action
of which the channel rapidly becomes deepened and
No mercury or riffles are employed in the ground
sluice, but unless the bottom consists of a rough and Irregular bed rock, some large stones should be roughly
thrown in for the purpose of arresting the gold, which,
if the surface were not uneven, would be liable to pass'
off and be lost.
In a river mining " the stream of a river is turned by'
means of a dam in connection with a ditch or large
wooden flume.    The dirt is subsequently washed.
The streams selected for this purpose are generally'
mere mountain torrents, of which the banks are steep
and irregular.
This sort of mining can only be successfully carried on'
Muring the summer and early fall, when the water is not'
only low, but when there is also no danger of a sudden
freshet which might sweep before it, flume, dam, and'
tools together. Hydraulic Mining.
In order to treat most successfully the extensive bed*
of detritus forming the deep placers, the following'conditions are involved:—
1. Whatever may be the depth of the auriferous grave!,
the whole must be removed down to the bed rock.
2. This must be effected by the force of a column of
water, manual labor being too expensive for the purpose.
3. The mechanical disintegration of the more or less
indurated gravel must go on at the same time as the
washing of the resulting debris, and be effected by the-
same supply of water.
4. Provision must be made for readily disposing of
the large amounts of refuse resulting from the removal
of Such vast masses of auriferous gravel.
To fulfil these conditions, after having selected a sufficient extent of suitable ground, water is brought from
a canal, by side flumes or aqueducts, to the head of
the. mining ground, with an elevation of from 120 to.
160 feet above the level of the bed rock, where it is
conducted into a wooden tank, into which it constantly
flows. This box is provided with a valve from which th*
water is conveyed to the bottom of the claim by means
of a strong sheet iron pipe, from eight to fourteen
inches in diameter, communicating at the bottom with a
thick rectangular cast iron chamber, in the sides of which
are apertures provided with slide valves and union joints,
to which are fitted strong flexible hose, terminating in
bronze nozzles from two and a half to three inches ii}
The hose are usually made of closely-sewn heavy
duck, and will, without external support, bear the pr& ■§
sure of a column of about fifty feet in perpendicular
height. When, as is frequently the case, the pressure
employed is greater than this, they require to be-
strengthened by iron rings. When so made, the hose
will support the pressure of a column a hundred and
eighty feet in height. Sometimes a netting of cord is
used instead of iron rings.
Streams of water are directed from the nozzles against
the face of the gravel to be washed, with a force which
is astonishing. Very often four or five such streams aio-'
made to act simultaneously, under a pressure of from.
60 to 100 pounds to the square inch, against the face of
the same bank.
Large masses of gravel are thus brought down, which
fall with violence, rendering it necessary for the workmen to exercise great caution to avoid accidents.
The debris thus produced becomes rapidly disintegrated-.
and is carried forward by the force of the water to the-
•luice, through which it passes with the whole volume of.
the turbid stream.
Banks of more than 80 feet in height are usually
worked in two benches.
The upper half is never so rich as the lower, but is, as
a rule, less compact and more easily removed by the action of the water. Sometimes the lo wer section is so
indurated that it requires the aid of gunpowder to loosen
The sluices employed in hydraulic mining are mads
wider than those used for other purposes, and are sometimes provided with wooden riffles, kept apart by slip*
of wood.   In some the bottoms are paved with stone.
The gold is collected in the cavities formed by th* -2 HYDRAULIC MIXIXG.
«iff.*rcnt broc.ts of wood constituting the riffles.    Between;
these riffle blocks quicksilver is placed.
Experience has proved that a larger proportion of the
precious metal is collected by this than by any other
process, and at the same time the cost of handling a
cubic vara of dirt is infinitely less.
As an evidence of the immense advantages of the
hydraulic process over every other system of placer
mining, it may be stated that the comparative cost of
handling a cubic yard of gravel will be nearly as.
With the pan $20 00.
"       rocker     5 00.
Bv h.vdraulic process         05. ^
Vein Mining,
Having given, it is hoped, a tolerably clear idea of the
various processes of gold washing, it is not proposed in
the present little treatise to furnish more than a short
description of the operations of vein mining, for the
subject of quartz, or vein mining, is one of such magnitude and importance, that justice could not be rendered
t) it without enlarging thia pamphlet to a size far exceeding that which was originally intended.
In vein mining, the miner undertakes through his own
skill and industry, by breaking up the original matrix
and extracting the rrecious metal which it encloses, to
effect that which, at some earlier period of the world's
history has, in placers, been done for him by nature on a
-gigantic scale.
The processes employed for the extraction of gold
quartz, are identical with the ordinary mining operations
in use for working regular mineral veins.
From the irregularit}' of the produce, it is impossible
to ascertain the average j'ield of a vein without crushing
and experimenting on large quantities.
But to judge, approximately, of the value of rock, a
small quantity is pounded up fine and sifted. The sieve
is examined to see if any flattened grains of gold remain
on it.
The sand or powder thus obtained is washed in a
shallow iron pan. Most of the gold is thus left in the
angle of the pan. By continuing this process upon
successive quantities of pulverized quartz, and when the
fculk lias been reduced to a manageable quantity, the Hi
jrold is amalgamated with quicksilver, the amalgam
»trained to separate excess of mercury, and finally heated
to expel the whole of it, leaving the gold.
After concentrating the gold in a smill quantity of
Mnd and pyrites, the residue may be subjected to the
fire assay, by which, of course, a much more accurate
result can be obtained than by amalgamation.
The processes employed for the extraction of gold are
various. The two priucipal methods are "amalgamation" and "chlorination."
Amalgamation in Arrastras.—This is an old method
tiscd by Mexican gold miners, but it gives tolerably good
results. It is useful for testing the value of newly dii-
•covered quartz veins.
The arrastra consists of a circular pavement of stone
•about twelve feet in diameter, on which the quartz ii
ground by means of large stones dragged in a circjlar
way by chains, fastened to four arms of a strong upright
wooden shaft.
One of these arms is made sufficiently loig to allow
mules to be attached for working the machine. Bound
ihe stone pavement are wooden sides about two feet in
Six to ten revolutions per minute are performed by the
blocks of stone, each of which weighs from three to four
linndred pounds. One and a half to two tons of rook,
which has been previously broken in pieces about the
iiiz«} of an og:^y can be ground in 24 hours.
The arrastra is charged with about two hundred
pounds of quartz, and is set in moiion, a little water
being added from time to time.
When the ore has assumed the. consistency of thick
•(•ream, quicksilver is sprinkled over its surface in tlw»
proportion of one ounce and a half for every ounce of
s£oid supposed to be contained in th- lock. VEIN MINING. 8p
•The then continued for about two hours.
When the amalgamation is considered complete, watefc
is admitted into the paste so as to render it thin, and
the machine is turned more slowly, to allow the particles
of gold and amalgam to sink to the bottom. AiKer
about half an hour the thin mud is allowed to run off,
leaving behind it, in the bottom of the arrastra, the gold
combined with the quicksilver in the form of amalgam.
Another charge of broken quartz is now put in and
treated in the same way, and so on till it is thought
desirable to stop to clean'up. Sometimes one hundred
to one hundred and fifty tons are thus worked through
in one " run."
Amalgamation in Iron Pans.—There are several
kinds of pans, named ^fter their different inventor?,
among which the Wheeler pan occupies a favorable
The two conditions, friction and contact with mercury,
are accomplished "in a high degree in this pan, by which
as much as 95 per cent, of the gold present is obtained.,
• Amalgamation *en the Battery.—The battery or.
stamping mill consists of a series of heavy pestles, work*
ing in a rectangular mortar, each of which is alternately
lifted by means of a cam, and then allowed to fall with
its own weight upon the quartz, which has been previously broken-upin small lumps. The number of blows
struck by each stamper is from 60 to 80 per minute.
- The ba'teries are provided with amalgamated copper
plates, three to five inches wid«', having the length of
the battery ; 'one on the feed side and the other at the
discharge, the former being protected by the iron feed
plate. They eM\ incline at an angle of 35 to 40 degrees
towards the.-stampeis
The quantity *of« quicksilver required depends upon the I
quantity of gold in the ore. Each ounce of gold takee
• ne, to one and a half, ounces of quicksilver, which is
introduced from time, to tbo feeder, during th«
By this process 60 to 75 per cent, of the. gold present
may be extracted.
In some places the rook is crushed without the use of
quicksilver in the mill.   The sand and water issuing frcm •
the battery are conducted over blankets spread on the
bottoms of shallow troughs, inclined at an angle of threo
or four degrees.    Beyond the blankets there are generally
riffles or amalgamated copper plates  to oaten  the gold
which may have escaped the blankets,
j The stampers are generally  kept at work day and
Iright, and the cleaning up of the battery takes place!
about once a week.
When quicksilver is used in the battery, a large pro*
portion of the gold obtained is taken from it in the form
of amalgam, and even when this metal is not introduced
a considerable percentage of the the produce is obtained
.a cleaning up. having accumulated in the cavitiea
around the dies in the shape of metallic spangles.
The coarser the gold iu the. rock, the larger is the
percentage of the total produce retained in the battery.
.The "Chlorinaiion process" gives satisfactory results
**ben the gold is in a finely-divided state. It is especially
used for ex'racting the gold from tailings, and is based
on the property of chlorine, of combining with gold,
forming terchloride of gold.
The tailings are first roasted to expel the sulphur,
arsenic* &c, sometimes a little salt or charcoal is added,
the former, however, causes a loss of gold.
• Alter six to right hours roasting the ore is spread'out
ro cool, and then sprinkled over with water and turned
ojrer till regularly and* suitably moistened. •VEIN MINING
The stuff is then introduced into tuos about sever!
feet in diameter and twenty-five or thirty inches deep..
•These tubs have false bottoms through which cmorofe
gas is allowed to enter into the mass of damp tailings'.
At the bottom of each tub are two holes, one for the* introduction of the chloriuef the other for running off tbto^
The gas is made from a mixture'of salt, peroxide &
manganese and sulphdric'acid, and the evolution is kept
up from twelve to fifteen hours, during whichftime tsn%
tubs are covered.
The covers are then removed and clean water introduced until it reaches the surface of the tailings, when
the discharge pipe is opened and the liquid, containing'
rhe dissolved chloride of gold, is drawn off into glass
Sulphate of iron is added, which precipitates the gold
as a brown powder, which is easily separated by decau-
tation and filtration, and then melted into bars which
are about 995 fine.
Let a represent the specific gravity of the metal.
|   D       u
u              u
CI                      (1
weight of the
4i                 It
a (c-b)
c (a-b)
The specific gravity of the metal and that of the stone
bave of course to be assumed, as they vary according to
As a general rule in these calculations the former is 28
taken at 19, the latter at 2.6. A convenient way of
taking the specific gravity when no apparatus is at band,
is to fill a glass vessel with water, to a mark. Then pour.
or draw off into another smaller vessel, so much of tjie
water as w ill alio w you freely to insert the specimen. A f ter
.this, fill up to the mark again, from the water drawn off'
The remainder of drawn water is exactly equal in bulk
to the specimen, the weight of that water, therefore,
gives the divisor, the weight of the dry specimen the
dividend; the quotient is its specific gravity aDSfcTSfife^iSi
Calculations of the Value of Gold,
In the Wnited States the value of gold' is based upon
the formula that 387 ounces of pure  gold are worth
,$8,000;   one  ounce  of pure gold  is  therefore   worth
• $20.6718346.
To find the value per ounce of gold of any give*
.fineness it is only necessary to multiply this sura by tl*a«
fineness required and divide by 1000.
I Thus, to find the value of American Standard, 900-
fine, multiply $20.6718346 by 900 and you obtaife
$18. 6046511.
In the United States Mints, the value of gold is calculated from the "standard" weight, viz; the weight of
the-bullion 900 fine,.
Forty-three ounces of standard gold are worth $800 -
therefore if the number of standard ounces are multiplied
by 800 and divided by 43 the value is obtained.
. For example, if it be desired to find the value of 268
ounces, 876 fine, multiply by 875 and divide by 900 to
obtain standard, then multiply by 800 and divide by 43
to arrive at the value in dollars:—   Thus:—
258 x 875 = 225750 Jjjj 225.75 ozs. of fine gold.   ;
225760 —: 900 = 250.83 ozs. of standard,
250.83 x 800 M 20066400.
'    20066400 —i—43 = $4666.60.
The "net" value of gold bullion is equal to the value
of the gold plus Vie value of the silver alloyed therewith, less the expense of coining and refining.
In refining, that is the separation^bf* the'silver frow
the gold, it has been found expedient in practice t$
f 30
leave a certain small proportion of silver in the gold, sinci
io extract the whole would be a much more expensive
operation, and, for commercial purposes, not a necessary
The amount of silver which is retained in the gold If
•equal to 1-99 of the weight of the fine gold, in other
words, the gold is refined to 990 fine.
It-is usual to assume in calculating the value of bullion,
that there are ten thousandths (.010) of base metal present.
The following examples will serve to explain the
■manner in which the net value of a deposit is obtained*
Supposing wo have a bar weighing  loo ozs.
gold 900 fine, value of the gold «.$1360.46
M ozs. pure silver, less 1—99 of 90 ozs. pore gold
equals .909, which, deducted from 9 ozs. pure
'  iiivi-r, equals 8.09 ozs. multiply this by the
value of pure silver, $1.2929, and the value *v
of the silver is ....*       10.4 (J
Premium on silver in  San Francisco Mints, 4
percent........ • .42
Value ot the gold and silver $ 1S71.34
Tied act charges: 8 cts. per oz. for refining, $8.00 »
i of 1 per cent for coining, $9.5 j ...........      17.S3
Vet value in gold coin at San Francisco...... $1853.99
In the preceding case the net 'mine in coin is $6.47
less than the value stamped on the bar, which is that of
the gold alone; it being the custom to look upon-the
silver as paying the expense of refilling and coining,*or
ra other words the conversion of the bullion into coin.   .
According to the proportion of the two metals the ael
talue varies. In the example above given there was a
toss.    We may take another eian ole in which the net CALCULATIONS OF THK VALU.E OF GOLD.    31
▼alue of the bar exceeds the stamped value of the gold,
owing to the lower fineness of the latter and consequent
larger proportion of silver. *
100 ozs. gold, 800 fine, value of the gold $1653.7*
19 ozs. pure silver, less 1-99 of 80 ozs. pure gold
• equals  .808,  which   deducted  from  19 ozs.
pure silver, equals 18.19 ozs. multiply thishy
$1.2929, and the value of the silver is        23.5»
Premium on silver in San Francisco, 4 per cent .94
Value of the gold and silver $1678.21
Deduct charges: 8 cts. per. oz. for refining, §8.00
. i of 1 per cent, for coining, &S.39       16 39
Net value in gold coin in San Francisco .$1661.82
■ Gain $8.07.
A simple method of calculating the value of the gold
and silver in a bar i3 to reduce the proportion to fine
gold and fine silver, and multiply by the value per oz.
of pure gold and pure silver.
For example a bar 2j0 ounces, 850 fine of gold, 140
fine of silver.
250 x 850 = 212£ ozs. pure gold, @ 20.6718, |ft $4352.75
260 x 140 = 35 ozs. pure silver, @ 1.2929, «-       45.25
Value of ^old and silver $4438 00-
: The above calculations give the Pan Francisco Mint
value of gold bars, that is the value of bars converted
in to .coin in San Francisco.
Besides this there is the commercial value.    Large
quantiiies of unrefined bullion are required-for expqrt*^
tion to Europe and the Eastern States, and the unpaited
gold may be said to vary in price like any other commodity according to thosugply and demand.
When-gold ba^rs are cited at 9C0 par, it means thaj. CA't'&OLAflulffS *UF TfiE YALtJE OF GOli>.
Ihe priee i* $18 60 per ounce, i. e. the value of gold dff
tin? fineness of 900: and bars of a lower fineness wculd
Command a premium while those having a higher fn.o-
ttess would be subject to a discount.
For every degree of fineness above par, 1-100 of 1
j-er a nt. is deductedj and for every degree of fitie>
rtess below the par rate,' 1-100 of 1 per cent, is added
»o the value of the bar.
Suppose 850 to be par. a bar 890 fine must be discounted 4-10 of 1 per cent, because it is deficient .040
in silver as compared with par rate. But if the bar be
% .0 fin j a premium of 4-10 of 1 per cent must be alio* -
ad, because it contains .040 of silver more than the par
rate requires.
In England the coinage of money is done by tl»**
♦Government without any charge, and the United States
Government has lately had under consideration the sub*
Jcct of either reducing the charge of •} of 1 per cent, or of
abolishing it altogether, with the view of stopping, as
fir as possible, the outflow of bullion, and increasing
the coinage of the country. If such a measure should
take effect, no doubt the export of bullion from the United
States would be to some extent checked, and the calculations of the value of gold given above would require
-**oi* modification. r
JL cubic inch of fine gold weighs 10.1509 ounces, and
is worth $209.84.
A cubic foot of the same is worth $362,600.
A cubic inch of United States Standard gold weighs
9.0989, and is worth $169,28.
A cubic foot of the same is worth $292,500.
The Troy ounce is equal to 480 grains.
The U. S. $20 piece weighs 5-16 grains.
The specific gravity of U. S. Standard gold is 17.3.     


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