stromeyerite, a sulfide mineral of copper and silver (CuAgS) that occurs as compact masses with copper and lead minerals in deposits at Altai, Siberia, Russia; Santiago, Chile; and Butte, Mont., U.S. Stromeyerite is a member of a group of sulfide minerals that form crystals of the isometric system at high temperatures but assume other symmetries upon cooling. The low-temperature form (below 93°C) of stromeyerite is orthorhombic. For detailed physical properties, see sulfide mineral (table).