Brassite

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Brassite
General
Category Arsenate mineral
Formula
(repeating unit)
Mg(AsO3OH)·4(H2O)
Strunz classification 08.CE.15
Dana classification 39.01.07.01
Crystal symmetry Orthorhombic dipyramidal
H-M symbol: (2/m 2/m 2/m)
Space group: P bca
Unit cell a = 7.472 Å, b = 10.891 Å, c = 16.585 Å; Z=8
Identification
Color White
Crystal habit Cryptocrystalline crusts
Crystal system Orthorhombic
Cleavage {001} Perfect
Fracture Irregular/uneven, splintery
Tenacity Brittle
Luster Silky, dull, earthy
Streak White
Diaphaneity Translucent
Specific gravity 2.28
Optical properties Biaxial (+)
Refractive index nα = 1.531 nβ = 1.546 nγ = 1.562
Birefringence 0.031
Pleochroism Non-pleochroic
2V angle 80°
Dispersion r < v moderate
Solubility +++ HCl, + H2O
References [1][2][3][4]

Brassite is a rare arsenate mineral with the chemical formula Mg(AsO3OH)·4(H2O). It was named brassite, in 1973, to honor French chemist R`ejane Brasse, who first synthesized the compound. The type locality for brassite is Jáchymov of the Czech Republic.[2]

It occurs as an alteration of magnesium carbonate minerals by arsenic bearing solutions. It occurs associated with pharmacolite, picropharmacolite, weilite, haidingerite, rauenthalite, native arsenic, realgar and dolomite.[3]

Localities[edit]

Czech Republic:

France:

Germany:

  • Wilhelm Mine (Wechselschacht), Bauhaus, Richelsdorf District, Hesse, Germany
  • Ore dumps, Richelsdorf Smelter, Süss, Richelsdorf District, Hesse, Germany

References[edit]