Getting Gold | Page 8

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