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a mineral; a green variety of chalcedony (see), with the color ranging from emerald green to grass and apple green, caused by microinclusions of nickel silicates. Chrysoprase has a vitreous or greasy luster. It is translucent and sometimes opalescent. In large segregations the degree of translucence and intensity of color varies. Chrysoprase occurs in the form of veins and veinlets in the weathering crust of ultrabasic rocks. Its formation is believed to be caused by hypergenic processes of chemical weathering of dunites and serpentinites or with the hydrothermal alteration of these rocks.
Chrysoprase is an attractive gem and semiprecious stone. It has been known and mined in Europe since the 14th century and was extensively used in the 17th and 18th centuries to make jewelry, church utensils, Florentine mosaics, and inlays. The largest deposit now being worked is at Marlborough in Australia; other deposits are found in Poland, the United States, and Brazil. In the USSR chrysoprase occurs in the Urals and in Kazakhstan.