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Colorless Synthetic Spinel
Synthetic spinel, already mentioned, is produced
in a vas, range of colors, designed to imitate one or another
of the better-known gems. Any such resemblance is always approximate,
although these stones sometimes have interesting characteristics
in their own right.
Appearance Yellow to yellow-green synthetic
spinel= (used to imitate chrysoberyl) are a lemon yellow shade
which generally turns greener in bright light, due to fluorescence.
The light green specimens (to imitate aquamarine are a cold,
wan color, which also turns greener in brigh* light. The blue-green
ones (to imitate zircon) have quite ar appropriate color,
midway between bright blue and paintbox green and very similar
to that of the natural gem. The blue ones (used to imitate
sapphire) have a striking cobaltblue tint not found in natural
sapphires. Those which change color from dark green to reddish
violet (used tc imitate alexandrite) are a very deep, often
almost blackisr, color, quite different from that of alexandrite.
They havE.•.a °. ° considerable luster, sometimes
better than that of the gems they are designed to imitate.
All the faceted cuts are
used and these are quite easily executed due to the gooo characteristics
of the material.
Distinctive features If blue synthetic spinel
is viewea from the table facet in strong tungsten light, the
facet edges of the pavilion display curious striae of red
fluorescence. The fact that it is singly refractive differentiates
the synthetic from most of the gems it is used to imitate.
Thus greenish blue and colorless spinel, which are used to
imitate zircon, do not show the obvious doubling of the facet
edges of the latter. When colorless spinel is used to imitate
diamond, it looks much less lustrous with very limited dispersion,
and is therefore quite readily distinguished. 'Furthermore,
in polarized light, the blurred, cross-hatched appearance
(due to anomalous birefringence) will immediately identify
it. Only in some cases is it possible to see under a microscope
the curved growth lines associated with the Verneuil process.
Minute gas bubbles are sometimes present as well, often being
tadpole-shaped or elongated and contorted.
Cost The price is always very low and mainly
depends on the cut.
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