Synthetic Gemstones in Jewelry

Synthetic corundum is cut nearly in all shapes in which natural corundum is cut. However, because of the low value of the rough material, a degree of mechanization can be used that was never possible with the rarer and more costly natural material: for this reason, cut synthetic stones are frequently more "mechanical" in appearance. Moreover, since they are used in inexpensive jewelry, standard sizes are encountered, sizes that are rarely seen, and then only by accident in natural stones. For instance, the cushion octagon brilliant cut (sometimes called the scissors cut) is rarely seen, if ever used for natural stones but very frequently for synthetics (as well as for imitations).

Linde Air Products Co. formerly employed lapidaries to fashion their synthetic star sapphires and rubies. An innovation encountered in that the stone-holding dop was mounted in a drill chuck with a flexible shaft, much like that used by dentists. Thus, when the stone was brought to bearer on lap, it was revolving at a uniform rate, instead of being revolved by hand, as with natural stones; this contributed to an exceptionally smooth polish, without the characteristics "orange-peel" effect and optical flats seen on many natural stones polished in the orient.

Novel forms in which synthetic corundum appears occasionally in jewelry include flame-polished rods and balls. By this polishing technique, which was developed in the United States, the rods and balls are rotated in an oxygen-gas flame that melts the surface slightly and obliterates the scratches. The method cannot be used for faceted stones, however.