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of
which is the disk for polishing, is inserted in these. The axle, and
thus the disk, is rotated by pushing back and forth upon it with the
right hand a long stick to which is fastened a string passing once
around the axle. The stone to be polished is held against this
revolving disk by the left hand, either with the fingers directly, or
by a stick to which the stone has been cemented. Abrasive powders and
water are contained in bowls made by sawing cocoanut shells in two, and
the abrasive is applied to the wheel by dipping the stone at intervals
into the mixture. By this painfully slow and laborious process the
polishing of the gem is in time accomplished.
Among
Occidental peoples, the cutting of gems was early carried to a much
higher point than among Orientals. By both Greeks and Romans gems were
given a symmetrical form, and they carried to a high degree of
perfection the art of cutting cameos and intaglios from them.
The
different forms into which precious stones are cut at the present time
may be arranged in two groups: (1), those having plane surfaces; and
(2), those having curved surfaces, although the two may be combined in
the same cutting. The different forms under these subdivisions may be
grouped, following Church, thus:
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Of
these cuttings, those of the first group are usually used for
transparent stones, such as the diamond, emerald, and ruby; and those
of the second for translucent and opaque gems, such as the opal,
turquois, moonstone, cat's-eye, and the like. The garnet is cut in both
ways, the cabochon-cut garnet being called a carbuncle.
The
question as to which form of cutting should be used for any particular
gem is one involving considerations of the mineral species and the
peculiarities of each individual stone. On the one hand, it is
desirable to avoid as little loss of the stone as possible; and on the
other, to give it that shape and proportion which shall best bring out
its luster, brilliancy, and color. Pale stones should, for instance,
have greater depth than dark ones; the latter should be given more
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