Anthonyite

Anthonyite is a hydrous secondary copper halide mineral with chemical formula of Cu(OH,Cl)₂·3(H₂O).

Anthonyite
Anthonyite from Mexico
General
Category	Halide mineral
Formula (repeating unit)	Cu(OH,Cl)2·3(H2O)
IMA symbol	Aty[1]
Strunz classification	3.DA.40
Crystal system	Monoclinic Space group unknown
Crystal class	Prismatic (2/m) (same H-M symbol)
Identification
Color	Lavender
Crystal habit	Prismatic crystals, commonly curved along [001]; as incrustations
Cleavage	{100}, good
Tenacity	Sectile
Mohs scale hardness	2
Diaphaneity	Translucent
Optical properties	Biaxial (-)
Refractive index	nα = 1.526 nβ = 1.602 nγ = 1.602
Birefringence	δ = 0.076
Pleochroism	X = rich lavender; Y = Z = deep smoky blue
2V angle	Measured: 3°
References	[2][3][4]

It was discovered in 1963 in the Centennial mine, Calumet, Houghton County, Michigan, United States. It was discovered by the University of Arizona mineralogist John W. Anthony (1920–1992), who named it for himself.

Anthonyite is lavender in color, has a Mohs hardness of 2 and crystallizes in the monoclinic crystal system.

Anthonyite occurs as an alteration of native copper in basalt in fractures and cavities by circulation of chloride rich groundwater or connate fluids. The similar orthorhombic mineral calumetite occurs by the same process. It occurs associated with tremolite, quartz, epidote, monazite, native copper, cuprite and paratacamite in the Centennial mine area. It also occurs in the Cole mine, at Bisbee, Cochise County, Arizona; and Villa Hermosa, Sonora, Mexico. It occurs as a slag mineral in Richelsdorf, Hesse, Germany and Laurium, Greece.[2][3]