A
is a handle which turns a large wheel on which runs an endless band
moving a smaller wheel, B, which turns the disk or skaif, C,—made of
various metals—at a high rate of speed. The lapidary turns the handle
with one hand, and with the other, supported by the rest, D, holds the
gem to be cut (firmly inserted on a cement-stick softened by heat)
against the disk, which is covered with the diamond-powder or emery,
according to the hardness of the stone. When one or two facets are
made, he again heats the cement, removes the stone, and refixes it,
exposing another part to the action of the wheel until the stone is
completed; for polishing, a similar wheel of lead, zinc, or wood, is
used with tripoli, rottenstone, vitriol, or rouge.
The
names of the various parts and facets of a coloured stone are
precisely the same as those of the diamond. The forms of the
brilliant, rose diamond, single-cut diamond, etc., have been already
described under the head of "Diamond ;" it is therefore only necessary
to describe the following, which are shown in the wood cuts. The first
is the
