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Synthetic ruby
This was the first synthetic gem to be manufactured
on an industrial scale and quantities have steadily increased
to the present day, the Verneuil method being the most widely
used.
Appearance Synthetic ruby is usually bright
red, differing very little from the natural stone, the physical
properties of which are also faithfully reproduced. It is
given the same oval, round or pear-shaped mixed, faceted cuts
or is made into cabochons. But it is also cut into special
shapes, often weighing 5-15 carats; for instance, rectangular
with a smooth, convex upper surface and faceted lower surface,
or with the top part convex, but consisting of numerous, juxtaposed
square facets and the bottom part faceted; or oval, again
with a smooth, convex upper surface and faceted lower surface.
These cuts are characteristic of synthetic rubies.
They are found in large stones that are highly
transparent, being completely free of inclusions, and are
often used for large, old-fashioned rings for men or set into
religious objects. Beads 2-3 to 7-8 millimeters in diameter
are also typical; of a perfectly even, bright red color and
uniform diameter, they are made into neckla::es and bracelets.
These pieces of jewelry could not possibly be made of natural
rubies. On the rare occasions when natural rubies are used
for this purpose, they are generally of mediocre color, full
of inclusions, and of graduated diameters. Fine quality natural
ruby is much too valuable to be treated ir this way.
Distinctive features These are almost exclusively
internal: generally speaking, this material is quite limpid
Provided one can find the right direction, thin (noncrystallographically
oriented) curved lines, characteristic of growth by deposition
of successive layers of molten material, will be visible under
a lens, or better still a microscope and sometimes, small
gas bubbles and "swarms" of minute, opaque foreign
bodies (unmelted alumina powder) can be seen. In the past,
a network of internal cracks was sometimes produced by a sudden
change of temperature to compensate for the suspicious absence
of inclusions The resulting stones appeared vaguely similar
to some natural rubies with numerous inclusions.
Cost Extremely low, bearing no relation to
that of their natural counterparts; in fact, most of the cost
of ordinary synthetic rubies is in the cutting. The rare synthetic
rubies produced by the flux melt or hydrothermal processes
are much more expensive, costing little less than the better
secondary gems. Hence, manufacture of these is not normally
economical. But given their resemblance to natural stones
and the possibility of some of them being sold as "good,"
there is a market for them. While sale of these stones invariably
starts out perfectly above board, it sometimes ends in a highly
profitable fraud after a few changes of hands, because of
the high value of natural rubies of similar characteristics.
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