can
hardly have the same top and back angles at every part of their
circumference. If the angle from a corner of a square stone is correct
then the angle from the middle of one side is obviously a little
different. Small differences of angle make considerable differences in
the brilliancy of cut stones. The prevailing tendency to cut nearly all
diamonds round depends largely upon the above facts. In the case of
colored stones, however, the added attractiveness which comes with odd
or different contour more than makes up for the slight loss of
brilliancy that may attend upon the shape selected. Such shapes as lend
themselves to special designs in mountings also justify any little loss
in brilliancy that accompanies the change in shape, provided the
proportions retained give a considerable amount of total reflection
within the stone and thus light up most of the stone as seen from the
front.

The test of the "make" of a color stone is its appearance. If it lights
up well over most of its surface and if the color is right, one should
not criticize the "make" as one would be justified in doing in the case
of a diamond. If, however, the effect is less attractive it would many
times be advisable to measure the angles of the stone, or its thickness
and spread as compared with similar measurements on a stone of fine
appearance. Frequently one will thus find the reason for the failure of
the stone to perform as it might, and recutting should be resorted to in
such cases in order to get a smaller but more beautiful and hence more
valuable stone.

LESSON XXIV

FORMS GIVEN TO PRECIOUS STONES

While precious stones are cut to many different forms, there are,
nevertheless, but a few general types of cutting. These may be
classified as follows: First, the "_cabochon_" (Fig. 11) type of
cutting; second, the old "_rose_" (Fig. 12) type of cutting; third, the
_brilliant_ (Fig. 13); fourth, the _step cutting_ (Fig. 14).

CABOCHONS. Of these the first, or _cabochon_ cutting, is probably the
most ancient. The term comes from a French word signifying a bald pate
(caboche, from Latin cabo, a head). The usual round cabochon cut closely
resembles the top of a head in shape. Cabochon cut stones usually have a
flat base, but sometimes a slightly convex base is used, especially in
opals and in moonstones, and some stones of very dense color are cut
with a concave base to thin them and thus to reduce their color. The
contour of the b