Star Gems
Another variation from regularity, which can scarcely be called an imperfection or a flaw, enhances the beauty and the value of a precious stone. A certain break or tiny space in the crystalline structure may produce a radiation of three lines crossing at a single point, giving the effect of a six-pointed star. The star ruby and the star sapphire are among the most highly prized of all gems.
The Pearl
The pearl has been described as “a disease of the oyster.” A tiny foreign object, such as a grain of sand or a chip off the inside of the shell (this inside is called nacre or mother-of-pearl) becomes imbedded in the oyster itself; it is, of course, an irritant. Drawing upon its natural resources but unable to expel the foreigner, the oyster protects itself by isolating the intruder, building around the speck a thin layer of an iridescent fluid, similar to that which lines the oyster shell. This fluid hardens, layer after layer. Given proper time—about four or five years—and the proper species of oyster—not the kind commonly used for food—and a pearl is born.
A cultured pearl differs from an imitation pearl much as a synthetic differs from a paste stone. A cultured pearl is naturally developed by an oyster which has been artificially inseminated. Man starts the process, the oyster carries it through. About 1920 an ingenious Japanese inserted a tiny bead of mother-of-pearl into an oyster; the result was the first cultured pearl. Since the oyster is first captured, then inoculated, then released under controlled conditions, the processes of production can be kept less haphazard, the time speeded and the quantity increased. As with synthetic gems, however, there are tiny indications, in structure, in lustrousness, by which the cultured may be distinguished from the native pearl.
Cutting the Stones
I have mentioned that the cutting may help to bring out the brilliance of a stone. There are two main types of cutting: the cabochon, used from earliest times; and the faceting, used increasingly over the past four centuries. Each is still valued for particular stones and purposes.