Hisingerite | |
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General | |
Category | Silicate mineral |
Chemical formula | Fe3+2Si2O5(OH)4·2H2O |
Strunz classification | 9.ED.10 |
Unit cell | a = 5.4 Å, b = 9.03 Å, c = 14.99 Å; β = 98.32°; Z = 4 |
Identification | |
Color | Black, brownish-black |
Crystal habit | Massive, compact; acicular, may be minutely spherical. |
Crystal system | Monoclinic |
Cleavage | None |
Fracture | Conchoidal |
Tenacity | Brittle |
Mohs scale hardness | 2.5 - 3.0 |
Luster | Vitreous, resinous, greasy |
Streak | Yellowish brown, green |
Diaphaneity | Transparent to translucent |
Specific gravity | 2.43 - 2.67 |
Optical properties | Biaxial (-) |
Refractive index | nα = 1.715 nγ = 1.730 |
Birefringence | δ = 0.015 |
References | [1][2][3] |
Hisingerite is an iron(III) phyllosilicate mineral with formula Fe3+2Si2O5(OH)4·2H2O. A black or dark brown, lustrous secondary mineral, it is formed by the weathering or hydrothermal alteration of other iron silicate and sulfide minerals.[1]
It was first described in 1828 for an occurrence in Riddarhyttan, Vastmanland, Sweden. It was named after Wilhelm Hisinger (1766-1852), a Swedish chemist.[3]
There are also aluminian hisingerite variety in which one of the iron atoms is replaced by aluminium and chrome-alumina-hisingerite variety in which chromium subtitutes for iron.[2]