Felsőbányaite

Felsőbányaite
General
Category Sulfate mineral
Formula
(repeating unit)
Al4(SO4)(OH)10·4H2O
Strunz classification 7.DD.05
Crystal symmetry Monoclinic sphenoidal
H-M symbol 2
Space group: P21
Unit cell a = 13.026 Å, b = 10.015 Å, c = 11.115 Å; β = 104.34°; Z=4
Identification
Color White to pale yellow, pale brown
Crystal habit Globular masses, minute rhombic crystals
Crystal system Monoclinic
Cleavage Distinct to good on {010} and {100}
Mohs scale hardness 1.5
Luster Vitreous, pearly on cleavage surfaces
Diaphaneity Semitransparent
Specific gravity 2.33
Optical properties Biaxial (+)
Refractive index n = 1.515–1.540
References [1][2]

Felsőbányaite or basaluminite is a hydrated aluminium sulfate mineral with formula: Al4(SO4)(OH)10·4H2O. It is a rare white to pale yellow mineral which typically occurs as globular masses and incrustations or as minute rhombic crystals. It crystallizes in the monoclinic crystal system.[2][1]

It occurs as a weathering product under acidic conditions associated with pyrite or marcasite decomposition. Associated minerals include hydrobasaluminite, hydroargillite, meta-aluminite, allophane, gibbsite, gypsum and aragonite.[2]

Felsőbányaite was first described in 1853 for an occurrence in the Baia Sprie mine, Baia Sprie (Felsőbánya), Maramureș County, Romania, and named for the locality.[1] The mineral name basaluminite was used for an occurrence of the same mineral in England in 1948 and discredited by the International Mineralogical Association (IMA) in 2006.[3]

References

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