EMERALD, a rich yellow-green to deep green variety of beryl (q.v.), a beryllium aluminum silicate. It is one of the most valuable of all gem stones (Rev 21:19) and owes its beauty to its color and transparency. “Fire,” such as shown by diamond, is lacking. The best emeralds are deep grass-green in color (4:3) and free from flaws, although unflawed emeralds are rare and large unflawed emeralds are unknown. Many crystals contain feathery inclusions while in some, the color, due to a small proportion of chromium is variable. Emerald mines were worked 2,000 years ago near the Red Sea, in Egypt, with hundreds of shafts sunk, some to 850 ft.; however the stones were not of fine gem quality. All the fine emeralds come from mines in Colombia, which were worked by the Spaniards. They occur in calcite (calcium carbonate) veins which cut across black shales.