GEM CUTS

Diameter is the most common measurement of size for size for cultured pearls, with the millimeter being used. Weight, though, may sometimes be used, including the carat, but two other terms are wore common. The weight of cultured pearls is measured in japanese mommes, with 1 momme equaling 18.75 carats, or about 3.75 grams. The number of pearls in a momme varies, de-g on the size of the pearls.

The larger the pearl, the more it weighs and the fewer pearls there are in a momme. It would -0 pearls, each 3 mm. in diameter, to make 1 momme, but 3 pearls, 9 mm. in diameter. Natural pearls are weighed by grains, with 4 grains equaling 1 carat. There are 75 grains to the momme. The weight of unstrung pearls, which tourists may buy in Japan, is more often given in mommes and grains than millimeters.

OTHER TERMS

Other terms that are helpful in buying jewelry with gems are used in connection with gem substitutes. Although the substitution sometimes be easily seen by the naked eye, it can be so good that sophisticated laboratory examination is necessary to detect it. In short, you can not always trust your eyes, and anyone who tries to show that a gem is genuine by holding it up to a light or a window is to be suspected.

Substitutes are nothing new. The earliest substitutes were glass, we ancient Egyptians, Greeks, and Romans were not above using glass gems" in jewelry. Less precious gems have also been used substitute for more precious gems. Other substitutes nowa days are man-made in the laboratory, thanks to advances in chemistry and physics.
Synthetic gems are man-made.

They are identical in chemistry and crystal structure to the natural gems they represent. In some cases, synthetic gems are so "real" that they even have the same kind of inclusions as the genuine gems. The first synthetic gems were rubies, which were synthesized in the 1880s and were sometimes called "Geneva rubies." !n 1904, August Verneuil introduced the Verneuil furnace, permitting mass production of synthetic gems. The crystals created are called boules.