Brassite

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.[3]

Brassite
Brassite (white) accompanied by rösslerite
General
CategoryArsenate mineral
Formula
(repeating unit)
Mg(AsO3OH)·4(H2O)
IMA symbolBsi[1]
Strunz classification8.CE.15
Dana classification39.01.07.01
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPbca
Unit cella = 7.472 Å,
b = 10.891 Å,
c = 16.585 Å; Z = 8
Identification
ColorWhite
Crystal habitCryptocrystalline crusts
Cleavage{001} Perfect
FractureIrregular/uneven, splintery
TenacityBrittle
LusterSilky, dull, earthy
StreakWhite
DiaphaneityTranslucent
Specific gravity2.28
Optical propertiesBiaxial (+)
Refractive indexnα = 1.531 nβ = 1.546 nγ = 1.562
Birefringence0.031
PleochroismNon-pleochroic
2V angle80°
Dispersionr < v moderate
Solubility+++ HCl, + H2O
References[2][3][4][5]

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.[4]

Localities

Czech Republic:

France:

Germany:

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

References


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