Emerald

Emerald, valuable green gemstone, a variety of the mineral beryl. Its beautiful color is attributed to the presence of a small amount of chromium. The best emeralds are mined in Muzo, Colombia. Good quality emeralds are also found in the Ural Mountains of the former USSR. Since 1946 synthetic emeralds have been made in the United States. They fluoresce deep red in ultraviolet light, whereas natural emeralds do not fluoresce.