68 PRECIOUS STONES
tion
bad shades of color are neutralized or modified. The darkness of some
green tourmaline crystals can be relieved by judicious cutting, and
from the double-colored crystals stones of different colors are
produced as they are cut with or across the grain, or they can be cut
to dichroic stones resembling the andalusite.
Although
stones of naturally dark color are necessarily cut thin to lighten
them, whenever the color is sufficiently fine to stand it a thick-cut
stone is better than a shallow one. A thin-cut colored stone is
inevitably weak or black-centred. Color can only be distributed evenly
by cutting thick, and a good night color can only be secured in the
alexandrite by cutting the stone full and deep.
As
a rule, the " step"-cut, in one of its many forms (see Plate XV.), is
most suitable. This has been improved somewhat of late by cutting the
upper portion with " brilliant" facets. Some object to the innovation,
but they certainly help the natural lustre of the stone and increase
its brilliancy.
Mr.
E. Passmore, of Boston, has succeeded in preserving the color and
enhancing the brilliancy of many fancy stones by cutting them entirely
" brilliant." In the course of his experiments he has perfected and
patented some very ingenious devices for securing, mechanically, right
proportions and exact facetings. This gentleman has done for colored
stones what Mr. Henry D. Morse did for diamonds,—viz., raised them in
the scale of beauty by improved methods of manipulation and cutting,
and he has shown that some of the finer specimens of the cheaper
varieties of stones may be made to rival in beauty others far more
costly.
The step-cut is a system of straight facets which decrease in length as they recede from the girdle.
Cabochon-cut
is flat with a polished convex top. It is the usual cut of opal,
cat's-eye, and turquoise. Rubies, sapphires, and emeralds are
sometimes so cut, and the carbuncle is simply a garnet cut en cabochon.
