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Synthetic Spinel
This is much the most common type of synthetic
spinel and is the main stone used to imitate aquamarine beryl.
Appearance The color varies
from soft pale blue to deep blue, but when viewed against
a white ground, it often has a grayish or violet-gray tinge.
It is perfectly transparent with strong luster. It is mainly
given faceted, step cuts, not always with truncated corners.
Mixed round, oval, and pear-shaped cuts are used as well.
Because synthetic spinel is hard but not brittle, extravagant
types of cuts are also possible, quite a frequent example
being one that is roughly star-shaped.
Another unusual cut often used on synthetic
spinel is the "scissors" cut, which is rectangular
in shape, an elongated cross linking the corners of the crown.
See fig. 31, page 72. Stones of all sizes are found, from
a fraction of a carat to 15-20 carats in weight.
Distinctive features The color,
due to cobalt, and therefore different from that of the natural
gem, can easily be distinguished by an expert. Single refraction
combined with a blurred, cross-hatched pattern due to anomalous
birefringence, which is very obvious in polarized light, is
distinctive of this and all synthetic spinels. It has greater
luster than the aquamarine it is intended to imitate. A star
or scissors cut in a light blue stone is a warning sign, although
not a sure indication, that the stone is synthetic.
Cost Very low and mainly due to the cutting
process.
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