A hard semiprecious stone consisting either of jadeite or nephrite. Jadeite, the most valued of the two, is a sodium aluminium pyroxene, NaAlSi2O6. It is prized for its intense translucent green colour but white, green and white, brown, and orange varieties also occur. The only important source of jadeite is in the Mogaung region of upper Burma. Nephrite is one of the amphibole group of rock-forming minerals. It occurs in a variety of colours, including green, yellow, white, and black. Sources include the Siberia, Turkistan, New Zealand, Alaska, China, and W USA.