Cafarsite
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.
| Cafarsite | |
|---|---|
 Cafarsite on granite | |
| General | |
| Category | Arsenites |
| Formula (repeating unit) | Ca8(Ti,Fe2+,Fe3+,Mn)6-7 (AsO3)12·4H2O |
| Strunz classification | 4.JC.05 |
| Crystal system | Isometric |
| Crystal class | Diploidal (m3) H–M Symbol (2/m 3) |
| Space group | Pn3 |
| Unit cell | a = 15.984 Å; Z = 4 |
| Identification | |
| Formula mass | 2,230.31 g/mol |
| Color | Dark brown |
| Crystal habit | Cubic/octahedral crystals |
| Fracture | Conchoidal |
| Mohs scale hardness | 5 1⁄2 - 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] |
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]
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