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Formula: Al2(SO4)(OH)4.7H2O
Hydrated sulphate, aluminite group
Crystal System: Monoclinic
Specific gravity: 1.7 measured, 1.794 calculated
Hardness: 1 to 2
Streak: White
Colour: White to yellow, grey; colourless in transmitted light
Solubility: Soluble in acids
Environments
Sedimentary environments
Hydrothermal environments
Aluminite occurs typically in clays or
lignites, formed by the reaction of sulphate-bearing solutions from
the decomposition of marcasite or
pyrite at moderate temperatures with
aluminous silicates, also as a volcanic sublimate and in
sulphur deposits, rarely in caves. Associated minerals include
felsőbányaite, gibbsite,
epsomite, gypsum,
celestine, dolomite and
goethite
(HOM).
Localities
At the type locality, Halle, Saxony-Anhalt, Germany, aluminite is found as earthy reniform or nodular masses
composed of tiny fibrous crystals
(Mindat).
Aluminite from Halle - Image
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