oot of the
"battery." The quartz is put in at the head of the battery, and is
gradually driven to the foot. The rotary stamps sometimes stand side by
side, and sometimes in a circle. The battery of both rotary and square
stamps is surrounded by wire gauze, or a perforated iron plate,
allowing the finely pulverized quartz to escape, and retaining the
coarser particles. Quartz is crushed wet and dry. In wet crushing a
little stream of water runs into the battery on one side and escapes on
the other, carrying all the fine quartz with it.

_Separation._--After pulverization comes the separation of the gold
from the rocky portion of the powder. The means of separation are
mechanical or chemical. The chemical process is amalgamation; the
mechanical are those wherein the gold is caught on a rough surface with
the aid of its specific gravity. The chief reliance is upon
amalgamation, and in some large quartz-mills mechanical appliances are
not used at all for catching the particles of gold, but only for
catching amalgam.

The mechanical appliances used in quartz-mills in separating the gold
from the pulverized rock, are the blanket, the sluice, and the raw
hide.

The blanket is a coarse, rough, gray blanket, which is laid down in a
trough sixteen inches wide and six feet long. The pulverized quartz is
carried over this by a stream of water, and the particles of gold are
caught in the wool. The blanket is taken up and washed, at intervals
depending upon the amount of gold deposited. In some mills where a
large amount of rock is crushed, and where the powder is taken over the
blanket before trying any other process of separation, the washing
takes place every half hour. In mills where the pulverized quartz is
exposed to amalgamation first, the blanket may be washed three or four
times a day. The washing is done in a vat, kept for that especial
purpose.

The sluice used in quartz-mills is similar to the placer board-sluice,
but the amount of matter to be washed is less, and there is no dirt to
be dissolved, and there are no larger stones, and therefore the sluice
is not so large, so strong, or so steep in grade, as the placer-sluice,
and the riffle-bars are not so deep. In some quartz-mill sluices there
are transverse riffle-bars. If the quartz has much iron or copper
pyrites, the sluice is used to collect this material and save it for
separation at some future time. The pyrites ordinarily contains, or is
accompanied by much