Cafarsite

Cafarsite

Cafarsite on granite
General
Category Arsenites
Formula
(repeating unit)
Ca8(Ti,Fe2+,Fe3+,Mn)6-7(AsO3)12·4H2O
Strunz classification 04.JC.05
Crystal symmetry Cubic diploidal H–M Symbol (2/m 3)
Unit cell a = 15.984 Å; Z = 4
Identification
Formula mass 2,230.31 g
Color Dark brown
Crystal habit Cubic/octahedral crystals
Crystal system Isometric
Fracture Conchoidal
Mohs scale hardness 5½ - 6
Luster sub-metallic
Streak Yellow brown
Diaphaneity Translucent to opaque
Specific gravity 3.9
Optical properties Isotropic
Refractive index n = 2.2
References [1][2][3]

Cafarsite (Ca8(Ti,Fe2+,Fe3+,Mn)6-7(AsO3)12·4H2O) is a rare calcium iron arsenite mineral. Manganese and titanium occur with iron in the formula.

It was first described in 1966 for an occurrence in the Binn Valley, Valais, Switzerland. Its name is from the composition, calcium, ferrum (iron), and arsenic.[2][1][3] It has also been reported from Piedmont, Italy and the Hemlo gold mine in the Thunder Bay District, Ontario, Canada.[3][2]

References