Getting Gold

J >> J. C. F. Johnson >> Getting Gold


To amalgamate with zinc amalgam, clean the copper plate by means of a
swab, with fairly strong sulphuric acid diluted with water; then while
wet apply the zinc-mercury mixture and well rub in. To prepare the
zinc-amalgam, clip some zinc (the lining of packing cases will do)
into small pieces and immerse them in mercury after washing them with
a little weak sulphuric acid and water to remove any coating of oxide.
When the mercury will absorb no more zinc, squeeze through chamois
leather or calico (as for silver amalgam), and well rub in. The plate
thus prepared should stand for a few days, dry, before using. If, before
amalgamation with gold takes place, oxide of copper or other scum should
rise on this plate a little very dilute sulphuric acid will instantly
remove it.

Sodium and cyanide of potassium are frequently used in dressing-plates,
but the former should be very sparingly employed, as it will often
do more harm than good by taking up all sorts of base metals with the
amalgam, and so presenting a surface which the gold will pass over
without adhering to. Where water is scarce, and is consequently used
over and over again, lime may be added to the pulp, or, if lime is not
procurable, wood ashes may be used. The effect is two-fold; the lime
not only tends to "sweeten" sulphide ores and keep the tables clean,
but also causes the water to cleanse itself more quickly of the slimes,
which will be more rapidly precipitated. When zinc amalgam is used,
alkalies would, of course, be detrimental.

When no other water than that from the mine is available, difficulties
often arise owing to the impurities it contains. These are various,
but among the most common are the soluble sulphates, and sometimes free
sulphuric acid evolved by the oxidisation of metallic sulphides. In the
presence of this difficulty, do one of two things; either _utilise_ or
_neutralise_. In certain cases, I recommend the former. Sometime since
I was treating, for gold extraction, material from a mine which was very
complex in character, and for which I coined the term "polysynthetic."
This contained about half a dozen different sulphides. The upper parts
of the lode being partially oxidised, free sulphuric acid (H2SO4) was
evolved. I therefore, following out a former discovery, added a little
metallic zinc to the mercury in the boxes and on the plates with
excellent results. When the free acid in the ore began to give out in
the lower levels I added minute quantities of sulphuric acid to the
water from time to time. I have since found, however, that with some
water, particularly West Australian, the reaction is so feeble (probably
owing to the lime and magnesia present) as to make this mode of
treatment unsuitable.

HOW TO MAKE A DOLLY

I have seen some rather elaborate dollies, intended to be worked with
amalgamating tables, but the usual prototype of the quartz mill is
set up, more or less, as follows: A tree stump, from 9 in. to a foot
diameter, is levelled off smoothly at about 2 ft. from the ground; on
this is firmly fixed a circular plate of 1/2 in. iron, say 9 in. in
diameter; a band of 3/16 in. iron, about 8 or 9 in. in height, fits
more or less closely round the plate. This is the battery box. A beam
of heavy wood, about 3 in. diameter and 6 ft. long, shod with iron,
is vertically suspended, about 9 in. above the stump, from a flexible
sapling with just sufficient spring in it to raise the pestle to the
required height. About 2 ft. from the bottom the hanging beam is pierced
with an augur hole and a rounded piece of wood, 1 1/2 in. by 18 in.,
is driven through to serve as a handle for the man who is to do the
pounding. His mate breaks the stone to about 2 in. gauge and feeds the
box, lifting the ring from time to time to sweep off the triturated
gangue, which he screens through a sieve into a pan and washes off,
either by means of a cradle or simply by panning. In dollying it
generally pays to burn the stone, as so much labour in crushing is thus
saved. A couple of small kilns to hold about a ton each dug out of a
clay bank will be found to save fuel where firewood is scarce, and will
more thoroughly burn the stone and dissipate the base metals, but it
must be remembered that gold from burnt stone is liable to become so
encrusted with the base metal oxides as to be difficult to amalgamate.

ROUGH WINDLASS

Make two St. Andrew's crosses with four saplings, the upper angle being
shorter than the lower; fix these upright, one at each end of the shaft;
stay them together by cross pieces till you have constructed something
like a "horse," such as is used for sawing wood, the crutch being a
little over 3 feet high. Select a leg for a windlass barrel, about 6 in.
diameter and a foot longer than the distance between the supports, as
straight as is procurable; cut in it two circular slots about an inch
deep by 2 in. wide to fit into the forks; at one end cut a straight slot
2 in. deep across the face. Now get a crooked bough, as nearly the shape
of a handle as nature has produced it, and trim it into right angular
shape, fit one end into the barrel, and you have a windlass that will
pull up many a ton of stuff.

PUDDLER

This is made by excavating a circular hole about 2 ft. 9 in. deep and,
say 12 ft. in diameter. An outer and inner wall are then constructed of
slabs 2 ft. 6 in. in height to ground level, the outer wall being thus
30 ft. and the inner 15 ft. in circumference. The circular space between
is floored with smooth hardwood slabs or boards, and the whole made
secure and water-tight. In the middle of the inner enclosure a
stout post is planted, to stand a few inches above the wall, and the
surrounding space is filled up with clay rammed tight. A strong iron pin
is inserted in the centre of the post, on which is fitted a revolving
beam, which hangs across the whole circumference of the machine
and protrudes a couple of feet or so on each side. To this beam are
attached, with short chains, a couple of drags made like V-shaped
harrows by driving a piece of red iron through a heavy frame, shaped as
a rectangular triangle.

To one end of the beam an old horse is attached, who, as he slowly walks
round the circular track, causes the harrows and drags to so puddle
the washdirt and water in the great wooden enclosure that the clay is
gradually disintegrated, and flows off with the water which is from time
to time admitted. The clean gravel is then run through a "cradle," "long
Tom," or "sluice," and the gold saved. This, of course, is the simplest
form of gold mining. In the great alluvial mines other and more
intricate appliances are used but the principle of extraction is the
same.

A MAKESHIFT PUMP

To make a temporary small "draw-lift" pump, which will work down to
a hundred feet or more if required, take a large size common suction
Douglas pump, and, after removing the top and handle, fix the pump as
close to the highest level of the water in the shaft as can be arranged.
Now make a square water-tight wooden column of slightly greater capacity
than the suction pipe, fix this to the top of the pump, and by means
of wooden rods, work the whole from the surface, using either a longer
levered handle or, with a little ingenuity, horse-power. If you can
get it the iron downpipe used to carry the water from the guttering of
houses is more easily adapted for the pipe column; then, also, iron pump
rods can be used but I have raised water between 60 and 70 feet with a
large size Douglas pump provided only with a wooden column and rods.

SQUEEZING AMALGAM

For squeezing amalgam, strong calico, not too coarse, previously soaked
in clean water, is quite as good as ordinary chamois leather. Some gold
is fine enough to escape through either.

MERCURY EXTRACTOR

The mercury extractor or amalgam separator is a machine which is very
simple in construction, and is stated to be most efficient in extracting
quicksilver from amalgam, as it requires but from two to three minutes
to extract the bulk of the mercury from one hundred pounds of amalgam,
leaving the amalgam drier than when strained in the ordinary way by
squeezing through chamois leather or calico. The principle is that
of the De Laval cream separator--i.e., rapid centrifugal motion.
The appliance is easily put together, and as easily taken apart. The
cylinder is made of steel, and is run at a very high rate of speed.

The general construction of the appliance is as follows: The casing or
receiver is a steel cylinder, which has a pivot at the bottom to receive
the step for an upright hollow shaft, to which a second cylinder of
smaller diameter is attached. The second cylinder is perforated, and
a fine wire cloth is inserted. The mercury, after passing through the
cloth, is discharged through the perforations. When the machine
is revolved at great speed, the mercury is forced into the outside
cylinder, leaving the amalgam, which has been first placed in a calico
or canvas bag, in a much drier state than it could be strained by hand.
While not prepared to endorse absolutely all that is claimed for this
appliance, I consider that it has mechanical probability on its side,
and that where large quantities of amalgam have to be treated it will be
found useful and effective.

SLUICE PLATES

I am indebted to Mr. F. W. Drake for the following account of sluice
plates, which I have never tried, but think the device worth attention:

"An addition has been made to the gold-saving appliances by the placing
of what are called in America, 'sluice plates' below the ordinary table.
The pulp now flows over an amalgamating surface, 14 ft. long by 4 ft.
wide, sloping 1 1/2 in. to the foot, and is then contracted into a
copper-plated sluice 15 ft. long by 14 in. wide, having a fall of 1 in.
to the foot. Our mill manager (Mr. G. C. Knapp) advocated these sluice
plates for a long time before I would consent to a trial. I contended
that as we got little or no amalgam from the lower end of our table
plates there was no gold going away capable of being recovered by copper
plates; and even if it were, narrow sluice plates were a step in the
wrong direction. If anything the amalgamating surface should be widened
to give the particles of gold a better chance to settle. His argument
was that the conditions should be changed; by narrowing the stream and
giving it less fall, gold, which was incapable of amalgamation on the
wide plates, would be saved. We finally put one in, and it proved
so successful that we now have one at the end of each table. The
per-centage recovered on the sluice plates, of the total yield, varies,
and has been as follows:--October, 9.1 per cent; November, 6.9 per cent;
December, 6.4 per cent; January, 4.3 per cent; February, 9.3 per cent."

MEASURING INACCESSIBLE DISTANCES

To ascertain the width of a difficult gorge, a deep river, or
treacherous swamp without crossing and measuring, sight a conspicuous
object at the edge of the bank on the farther side; then as nearly
opposite and square as possible plant a stake about five feet high, walk
along the nearer margin to what you guess to be half the distance across
(exactitude in this respect is not material to the result), there plant
another stake, and continuing in a straight line put in a third. The
stakes must be equal distances apart and as nearly as possible at a
right angle to the first line. Now, carrying in hand a fourth stake,
strike a line inland at right angles to the base and as soon as sighting
over the fourth stake, you can get the fourth and second stakes and
the object on the opposite shore in line your problem is complete. The
distance between No. 4 and No. 3 stakes is the same as that between No.
1 and the opposite bank.

TO SET OUT A RIGHT ANGLE WITH A TAPE

Measure 40 ft. on the line to which you wish to run at right angles, and
put pegs at A and B; then, with the end of the tape held carefully at
A, take 80 ft., and have the 80 ft. mark held at B. Take the 50 ft. mark
and pull from A and B until the tape lies straight and even, you will
then have the point C perpendicular to AB. Continue straight lines by
sighting over two sticks in the well-known way.

_Another method_.--Stick a pin in each corner of a square board, and
look diagonally across them, first in the direction of the line to which
you wish to run at right angles, and then for the new line sight across
the other two pins.

A SIMPLE LEVELLING INSTRUMENT

Fasten a common carpenter's square in a slit to the top of a stake by
means of a screw, and then tie a plumb-line at the angle so that it
may hang along the short arm, when the plumb-line hangs vertically
and sights may be taken over it. A carpenter's spirit-level set on an
adjustable stand will do as well. The other arm will then be a level.

Another very simple, but effective, device for finding a level line is
by means of a triangle of wood made of half-inch boards from 9 to 12
ft. long. To make the legs level, set the triangle up on fairly level
ground, suspend a plummet from the top and mark on the cross-piece where
the line touches it. Then reverse the triangle, end for end, exactly,
and mark the new line the plumb-line makes. Now make a new mark exactly
half way between the two, and when the plumb-line coincides with this,
the two legs are standing on level ground. For short water races this is
a very handy method of laying out a level line.

TO MEASURE THE HEIGHT OF A STANDING TREE

Take a stake about your own height, and walking from the butt of the
tree to what you judge to be the height of the timber portion you want,
drive your stake into the ground till the top is level with your eyes;
now lie straight out on your back, placing your feet against the stake,
and sight a point on the tree. AB equals BC. If BC is, say 40 ft., that
will be the height of your "stick of timber." Thus, much labour may be
saved in felling trees the timber portion of which may afterwards be
found to be too short for your purpose.

LEVELLING BY ANEROID BAROMETER

This should be used more for ascertaining relatively large differences
in altitudes than for purposes where any great nicety is required.
For hills under 2000 ft., the following rule will give a very close
approximation, and is easily remembered, because 55 degrees, the assumed
temperature, agrees with 55 degrees, the significant figures in the
55,000 factor, while the fractional correction contains _two fours_.

Observe the altitudes and also the temperatures on the Fahrenheit
thermometer at top and bottom respectively, of the hill, and take the
mean between them. Let B represent the mean altitude and b the mean
temperature. Then 55000 X B - b/B + b = height of the hill in feet for
the temperature of 55 degrees. Add 1/440 of this result for every degree
the mean temperature exceeds 55 degrees; or subtract as much for every
degree below 55 degrees.

TO DETERMINE HEIGHTS OF OBJECTS

_By Shadows_

Set up vertically a stick of known length, and measure the length of its
shadow upon a horizontal or other plane; measure also the length of
the shadow thrown by the object whose height is required. Then it will
be:--As the length of the stick's shadow is to the length of the stick
itself, so is the length of the shadow of the object to the object's
height.

_By Reflection_

Place a vessel of water upon the ground and recede from it until you see
the top of the object reflected from the surface of the water. Then it
will be:--As your horizontal distance from the point of reflection is
to the height of your eye above the reflecting surface, so is the
horizontal distance of the foot of the object from the vessel to its
altitude above the said surface.

_Instrumentally_

Read the vertical angle, and multiply its natural tangent by the
distance between instrument and foot of object; the result is the
height.

When much accuracy is not required vertical angles can be measured by
means of a quadrant of simple construction. The arc AB is a quadrant,
graduated in degrees from B to A; C, the point from which the plummet P
is suspended, being the centre of the quadrant.

_When_ the sights AC are directed towards any object, S, the degrees
in the arc, BP, are the measure of the angle of elevation, SAD, of the
object.

TO FIND THE DEPTH OF A SHAFT

_Rule_:--Square the number of seconds a stone takes to reach the bottom
and multiply by 16.

Thus, if a stone takes 5 seconds to fall to the bottom of a shaft--

5 squared = 25; and 25 X 16 = 400 feet, the required depth of shaft.

DESCRIPTION OF PLAN FOR RE-USING WATER

Where water is scarce it may be necessary to use it repeatedly. In a
case of this kind in Egypt, the Arab miners have adopted an ingenious
method which may be adapted to almost any set of conditions. At a is a
sump or water-pit; b is an inclined plane on which the mineral is washed
and whence the water escapes into a tank c; d is a conduit for taking
the water back to a; e is a conduit or lever pump for raising the
water. A certain amount of filtration could easily be managed during the
passage from c to a.

COOLING COMPOUND FOR HEATED BEARINGS

Mercurial ointment mixed with black cylinder oil and applied every
quarter of an hour, or as often as expedient. The following is also
recommended as a good cooling compound for heavy bearings:--Tallow 2
lb., plumbage 6 oz., sugar of lead 4 oz. Melt the tallow with gentle
heat and add the other ingredients, stirring until cold.

CLEANING GREASY PLUMMER BLOCKS

When, through carelessness or unpreventable cause, plummer blocks
and other detachable portions of machinery become clogged with sticky
deposits of grease and impurities, a simple mode of cleansing the same
is to take about 1000 parts by weight of boiling water, to which add
about 10 or 15 parts of ordinary washing soda. Keep the water on the
boil and place therein the portions of the machine that are to be
cleaned; this treatment has the effect of quickly loosening all grease,
oil, and dirt, after which the metal is thoroughly washed and dried. The
action of the lye is to form with the grease a soap soluble in water. To
prevent lubricating oil hardening upon the parts of the machinery when
in use, add a third part of kerosene.

AN EXCELLENT ANTI-FRICTION COMPOUND

For use on cams and stamper shanks, which will be harmless should it
drop into the mortar or stamper boxes, is graphite (black-lead) and
soft soap. When the guides are wooden, the soft soap need not be added;
black-lead made into a paste with water will act admirably.

TO CLEAN BRASS

Oxalic acid 1 oz., rotten stone 6 oz., powdered gum arabic 1/2 oz.,
sweet oil 1 oz. Rub on with a piece of rag.

A SOLVENT FOR RUST

It is often very difficult, and sometimes impossible, to remove rust
from articles made of iron. Those which are very thickly coated are
most easily cleaned by being immersed in a nearly saturated solution
of chloride of tin. The length of time they remain in this bath is
determined by the thickness of the coating of rust. Generally from
twelve to twenty-four hours is long enough.

TO PROTECT IRON AND STEEL FROM RUST

The following method is but little known, although it deserves
preference over many others. Add 7 oz. of quicklime to 1 3/4 pints
of cold water. Let the mixture stand until the supernatant fluid is
entirely clear. Then pour this off, and mix with it enough olive oil
to form a thick cream, or rather to the consistency of melted and
re-congealed butter. Grease the articles of iron or steel with this
compound, and then wrap them up in paper, or if this cannot be done,
apply the mixture somewhat more thickly.

TO KEEP MACHINERY FROM RUSTING

Take 1 oz. of camphor, dissolve it in 1 lb. of melted lard; mix with
it (after removing the scum) as much fine black-lead as will give it an
iron colour; clean the machinery, and smear it with this mixture. After
twenty-four hours rub off and clean with soft, linen cloth. This mixture
will keep machinery clean for months under ordinary circumstances.

FIRE-LUTE

An excellent fire-lute is made of eight parts sharp sand, two parts good
clay, and one part horse-dung; mix and temper like mortar.

ROPE-SPLICING

A short splice is made by unlaying the ends of two pieces of rope to a
sufficient length, then interlaying them, draw them close and push the
strands of one under the strands of the other several times. This
splice makes a thick lump on the rope and is only used for slings,
block-straps, cables, etc.