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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