The Emerald:
Emerald, the most valuable of gems, is a transparent variety of the beryllium aluminosilicate mineral Beryl that owes its bright green color to small amounts of chromic oxide. Large, flawless stones are very rare. Lacking the fire and brilliance of diamond, emerald is usually step cut, with elongated narrow facets and an oblong table, to enhance its color. Emeralds have been obtained from the schists of Cleopatra's mines, rediscovered in 1818, in the Sikait-Zubara region of Egypt. Vast quantities were taken from South America during the Spanish conquest, but the original mines have since been lost.
The finest stones come from Colombia, where they are mined from the calcite veining bituminous limestone at Muzo, Cosauez, and Somondoco, Bogota; these deposits were discovered in the late 1500s. Emeralds were discovered in 1830 in mica schists near Sverdlovsk, in Russia's Ural Mountains. They have been produced artificially by using a process developed by Carroll F. Chatham in the 1930s.
The emerald of the ancients probably referred to a number of distinct species of green stones; that mentioned in the Old Testament probably was carbuncle garnet. Superstitions abound concerning the emerald, birthstone for May: it supposedly soothes the eyes, preserves chastity, cures dysentery, prevents epilepsy, drives away evil spirits, and facilitates childbirth.
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