Hisingerite

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Hisingerite
Hisingerite-282352.jpg
Crystallized plates of reddish-brown, silver metallic-lustre hisingerite crystals
General
CategorySilicate mineral
Formula
(repeating unit)
Fe3+2Si2O5(OH)4·2H2O
Strunz classification9.ED.10
Crystal systemMonoclinic
Unknown space group
Unit cella = 5.4, b = 9.03
c = 14.99 [Å]; β = 98.32°; Z = 4
Identification
ColorBlack, brownish-black
Crystal habitMassive, compact; acicular, may be minutely spherical.
CleavageNone
FractureConchoidal
TenacityBrittle
Mohs scale hardness2.5 - 3.0
LusterVitreous, resinous, greasy
StreakYellowish brown, green
DiaphaneityTransparent to translucent
Specific gravity2.43 - 2.67
Optical propertiesBiaxial (-)
Refractive indexnα = 1.715 nγ = 1.730
Birefringenceδ = 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 substitutes for iron.[2]

References[edit]