SOUVENIR-CHARTERS TOWERS, 1872 TO JULY, 1950
Page 7
METHOD OF TREATMENT
MOST of the ore produced was treated at the local crushing mills. These
were of the stamper type battery. The ore being fed from the hoppers
through a stone cracker and then conveyed to another hopper from which
it was
fed into the stamper boxes. These boxes contain water and the stamper
crushes the stone into pulp, which is forced through a very fine wire
woven screen. The first gold recovered comes from these boxes which are
charged with mercury to catch the free or coarse gold. The pulp is then
washed over copper plates which are charged with mercury (or
quicksilver) attracts the gold and these plates are scrubbed and the
mercury squeezed into amalgam balls which are later retorted. The
mercury going off in a vapour from the retort pot once it meets the
cool air, is recovered in its original form. After the pulp leaves the
gold tables (that is the copper plates) it is run through launders and
then goes over what is called a "Wilfley Table." This table has a
perpetual shaking movement and the "Mineral Content" of the pulp, which
is called concentrates and is much heavier than the residues or sands
is shaken to the extreme edge of the body of pulp passing over the
Wilfley table and is guided into a special vat. These concentrates
usually contain a high percentage of the gold output of the stone
and as a rule are sent to the smelters for treatment.
The residues or sands after passing over the Wilfley table are either
dumped or lifted, by some means and carried away into large vats or
settling pits. (This method was used in the earlier days and is still
used in some
mills today although modern methods of cyanidation would
obviate some of the handling necessary under this method of
treatment.) From these settling pits the sands are carted out on to a
flat, where they are spread and dried, and rolled. The sands are then
carted back and placed in large vats (cyanide vats) where a cyanide
solution is poured into the vats and percolates through
the sands and this solution is then drained by means of an outlet valve
through pipes, where it then flows through a series of boxes, charged
with zinc shaving. These shavings attract the gold
content from the solution, and eventually the shavings are
roasted and then smelted when a gold bullion is recovered. This
bullion is again smelted and by the use of certain fluxes, all
impurities are taken off leaving the gold bar. For the benefit of those
who have not witnessed the pouring of the molten gold from the
smelting pot into the cast iron moulds, I would say there is no better
sight. An orange flame pours forth into the mould, the gold being the
heavier substance goes to the bottom and the fluxes and impurities
form a crust on the top. This is referred to as the slag.
PYRITES WORKS
THE results were very satisfactory and although the directors were a
very economical body of men, the
credit for the success really belonged to their Manager, Mr. Brown.
The process used included calcinating and chlorinating the percentage
of gold extracted being as high as 97 per cent. in some cases.
At the time at least a dozen or more mines on the Towers field sent
their tailings to the works, but there were a few men who would do
anything but patronise a local institution and would send their
tailings overseas for treatment, and in many cases after paying
freight and treatment charges, the value of the gold won would show a
loss to the owners, who did not patronise their local works.
The cyanide process was eventually responsible for the closing of the
Pyrites Works, although the Australian Gold recovery works
(cyanide agents for McArthur Forrest the discoverers of cyanide
process) was operating for a
