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.[2]
| Brassite | |
|---|---|
 Brassite (white) accompanied by rösslerite | |
| General | |
| Category | Arsenate mineral |
| Formula (repeating unit) | Mg(AsO3OH)·4(H2O) |
| Strunz classification | 8.CE.15 |
| Dana classification | 39.01.07.01 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pbca |
| Unit cell | a = 7.472 Å, b = 10.891 Å, c = 16.585 Å; Z = 8 |
| Identification | |
| Color | White |
| Crystal habit | Cryptocrystalline crusts |
| 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] |
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
Czech Republic:
- Jáchymov (St Joachimsthal), Jáchymov, Krušné Hory Mts (Erzgebirge), Karlovy Vary Region, Bohemia, Czech Republic
France:
- Salsigne mine, Salsigne, Mas-Cabardès, Carcassonne, Aude, Languedoc-Roussillon, France
- Villanière (slag locality), Salsigne, Mas-Cabardès, Carcassonne, Aude, Languedoc-Roussillon, France
Germany:
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