Group of colourless rösslerite crystals on white brassite from the famous locality of Jachymov (Bohemia, Czech Republic). — Photo: David Hospital · CC BY-SA 4.0
Brassite
A rare hydrated magnesium arsenate named in 1973 for French chemist Réjane Brasse, who first synthesized it.
Intro adapted from Wikipedia (CC BY-SA).
Brassite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Mg(AsO₃OH)·4H₂O.
It crystallizes in the orthorhombic crystal system (space group Pbca).
Key properties: specific gravity 2.28; Pearly luster; refractive index 1.546; optically biaxial.
IMA symbol Bsi, IMA status: approved, named in 1973.
A rare reaction product of arsenic-rich solutions with Ca–Mg carbonates.
It is found associated with Pharmacolite, picropharmacolite, weilite, haidingerite, rauenthalite, arsenic, realgar, dolomite.
The mineral was named to honor Rèjane Brasse, who first synthesized the compound.