Mineral Species: Fornacite

Chemical Formula: Pb2Cu(CrO4)(AsO4)(OH)

Chemical Name: Lead Copper Chromate Arsenate Hydroxide

Mineral Class: Arsenate 

Mineral Notes: Fornacite is a rare mineral in the oxidized zones of some hydrothermal base-metal deposits. The species was first recognized in the 1950s when a single pocket at the Mammoth Mine was discovered containing some of the world’s largest Fornacite crystals associated with Wulfenite. The mineral is named after Lucien Louis Forneau (1867–1930), Colonial Governor of the French Congo.

Description: Dark, prismatic crystals of Fornacite on matrix. The mineral has a very strong glassy luster. Associated with the Fornacite are pale blue-green Chrysocolla and Chabazite which cover one side of the matrix.

Location: Mammoth Mine, Tiger, Pinal Co., Arizona, USA. (Type Location)