Wulfenite: Gemstones Information
s and crystal groups of the tetragonal system.Individual crystals are usually square, flat tabular with resinous to subadamantine to adamantine lustre. The hardness is 2.5–3 and the SG 6.5–7.0. The RI for the ordinary and extraordinary rays is 2.405 and 2.283, uniaxial negative (may be biaxial) with birefringence 0.122.Wulfenite occurs as a secondary mineral formed in the oxidized zone of hydrothermal lead deposits with the Mo commonly introduced externally. The finest specimens are the near-red specimens from the Red Cloud mine, Silver District, La Paz County, Arizona, USA, and similar specimens from the Glove mine, near Amado, Tyndall district, Santa Cruz County in the same state. Fine examples have also come from Bleiberg, Carinthia, Austria.