Cafarsite

Cafarsite (Ca
8
(Ti,Fe2+
,Fe3+
,Mn)
6–7
(AsO
3
)
12
·4H
2
O
) is a rare calcium iron arsenite mineral. Manganese and titanium occur with iron in the formula.

Cafarsite
Cafarsite on granite
General
CategoryArsenites
Formula
(repeating unit)
Ca
8
(Ti,Fe2+
,Fe3+
,Mn)
6–7
(AsO
3
)
12
·4H
2
O
Strunz classification4.JC.05
Crystal systemIsometric
Crystal classDiploidal (m3)
H–M Symbol (2/m 3)
Space groupPn3
Unit cella = 15.984 Å; Z = 4
Identification
Formula mass2,230.31 g/mol
ColorDark brown
Crystal habitCubic/octahedral crystals
FractureConchoidal
Mohs scale hardness5 12 - 6
Lustersub-metallic
StreakYellow brown
DiaphaneityTranslucent to opaque
Specific gravity3.9
Optical propertiesIsotropic
Refractive indexn = 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]

References

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