contained
gold though it was not visible to the eye, and that by roasting the
mineral they would get it. In one locality it was usual for the miners
to procure blocks of pyrites, divide them, and take the pieces to their
homes for treatment.
In
breaking up blocks of quartz too on the outcrops of the reefs, it is
said that they used fire. In one place, according to information given
to me, the trees of the jungle were felled, the timber piled in heaps
on the quartz and there burnt, and on the outcrop of one reef an
excavation in the solid rock was found which appeared to have been
constructed for and used as a kiln.
Where
the quartz miners have labored there are to be seen usually large heaps
of broken quartz, the pieces rejected because they did not show gold;
and on the out crops of the reefs are found the smooth hollows in the
rocks worn by long hand-grinding, while in the jungles, the flat stones
and mullers, covered with moss, are occasionally met with.
It
may be interesting to remark that these flat stones and mullers are
very similar in form to those used by the Australian natives for
grinding seeds, &c.
The
miners who worked in the adits seem to have had more knowledge of
mining and of the modes of occurrence of gold than those who formerly
got out quartz by sinking vertical shafts. The former followed the run
of gold wherever they were able to do so, sometimes taking out the
foot-wall and "casing" and sometimes the hanging wall.
The
Korumbars, skilful as they are, have no knowledge of the manner in
which the gold has been distributed. They are acquainted with the "run"
of the reefs and show great intelligence in selecting spots likely to
yield gold, but they do not believe that the gold in the* soils has
been derived from the disintegration of the reefs. They say that it is
found in some places in the reefs, in other places in the soils, but
that its occurrence in the latter is in no manner connected with the
former.
Machinery for treating auriferous quarts, &*c.—The
machinery and appliances for crushing auriferous quartz and saving gold
are simple in themselves and easily managed when the principles on
which they are designed are understood. Neither that portion of the
work of reduction which is purely mechanical, bringing the mineral into
such a state as to admit of metallurgical treatment, nor the
metallurgical treatment itself is of such a character as to call for
more than the knowledge which is to be gained in any large
quartz-crushing establishment. A competent superintendent may not be
an engineer nor a chemist, but he should have a sufficient acquaintance
with mechanics and mechanical processes, and he should be familiar at
least with the chemistry of the metals and minerals with which he has
to deal.
The
machine for crushing quartz consists of a series of stamp-heads
arranged in batteries of four or five. To each stamp-head is attached
a lifter with a circular disc. A horizontal shaft, provided with wipers
(so placed as to catch the discs) when put in motion causes the
stamp-heads to act as so many pestles. The wipers are arranged in such
a manner as to make the stamp-heads in each battery fall successively,
but the order in which they fall is not the same in all mills; and each
stamp-head rotates, making part of a revolution each time that the
wiper catches the disc.
The
stamp-head moves in an iron box or coffer having spaces covered with
perforated plates for the passage of the crushed quartz. The bottom qf
the coffer is packed with broken quartz to the depth of three inches,
and on the broken stone lies the false bed of wrought iron.
In
the best mills the stamp-head with its shank or lifter weighs from 6
cwt. to 8 cwt., in some the weight is as low as 2 cwt., and in others
as high as 9 cwt. The height the head falls varies from 6 inches to 15
inches, and in the number of blows per rainute there is a wide range;
in one mill the number may be no more than 45, and in other 85.
