p
color in a short time.

The whitened zircon, when finely cut in the brilliant form, with truly
flat facets and sharp edges and with a top angle of about 39 degrees and
a back angle of about 44 degrees, so closely resembles a diamond that it
will deceive almost anyone on casual inspection. The expert, even, may
be deceived, if caught off his guard. The writer has a fine specimen of
a little over one carat, with which he has deceived many jewelers and
pawnbrokers, and even an importer or two. If it is presented as a stone
that closely resembles diamond your expert will say: "Yes, it is pretty
good, but it would never fool me." If, however, you catch him off his
guard by suggesting, perhaps, "Did you ever see a diamond with a
polished girdle?", then he will look at it with interest, remark on its
fine color and "make," and never think of challenging its character.

The refractive index of the dense type of zircon is so high (1.92-1.98)
that it lights up well over most of the surface of the brilliant when
cut, as above indicated, and does not show markedly the weak dark center
shown by white sapphire, white topaz, colorless quartz, colorless beryl,
and paste, when seen from the side. Moreover, the luster of zircon is
nearly adamantine, so the expert does not miss the cold metallic glitter
as he would with any other white stone. The color dispersion, too, is so
high (86% as great as in diamond) that the zircon has considerable
"fire," and thus the casual handler is again deceived. A fine white
zircon is really prettier than a _poor_ diamond. It cannot compare,
however, with a _fine_ diamond. It would never do to let an expert see
your zircon beside even a fair diamond. The zircon would look "sleepy."
It is only when no direct comparison is possible, and when the expert is
not suspicious, that a zircon can deceive him. Of course, the use of the
scientific tests of the earlier lessons will, at once, detect the
character of a whitened zircon. The hardness is but 7.5, the refraction
so strongly double that the edges of the back facets appear double-lined
when viewed through the table with a lens, and the specific gravity is
4.69. Double spots of light appear on the card when the sunlight-card
test is applied. Hence, it is easy to detect zircon by any of these
tests if there is reason to suspect that it has been substituted for
diamond.

CORUNDUM GEMS. Rubies of streaky color are said to be improved by
careful heating. Usual