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Cubic Zirconia
These names refer mainly to the colorless variety
used as a substitute for diamond. Cubic zirconia looks very
similar to diamond and is now much the most widely used diamond
simulant.
Appearance It is perfectly transparent and
colorless, highly lustrous, and when cut into brilliants or
related pearshaped, oval or marquise fancy cuts is extremely
similar to diamond, while step-cut stones look a bit duller.
Its good hardness, plus the fact that it is isotropic, means
that it can be cut with great precision, giving sharp facet
edges, like those obtainable with diamond.
Distinctive features To the practiced eye,
brilliant cut stones show slightly higher dispersion (or fire)
than diamond in bright light. Because the retractive index
is a bit lower than that of diamond, total internal reflection
is limited in cut stones; thus, if they are viewed from above
and tilted gradually, a dark area will be visible at a certain
point through the table facet, corresponding to some of the
pavilion facets which, instead of reflecting the light, are
letting it through. Sometimes, the girdle has a distinctive,
diagonally striated, transparent appearance, unlike that of
a diamond. In the case of a loose stone, particularly one
of some size, e.g., 9-10 millimeters in diameter, one can
feel the density of this material, which is almost double
that of diamond, merely by weighing it in the hand. Cubic
zirconia is also hard, but less so than corundum, against
which it can be tested if need be. This must be done cautiously,
however, under a microscope, to avoid undue damage to the
stone.
Cost Very low, mainly due to
the cutting process; about the same as that of modern synthetic
spinels and corundums.
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