Anorpiment (Size 37 mm x 24 mm x 22 mm) Locality: Palomo Mine, Castrovirreyna Province, Huancavelica Department, Peru Original description: An unusual pseudomorph of Anorpiment crystals after Realgar crystals on grey Galena. JSS specimen and photo. — Photo: John Sobolewski (JSS) · CC BY 3.0
Anorpiment
Anorpiment is an IMA-recognized mineral species in the sulfide class, with the chemical formula As₂S₃.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 1.5; specific gravity 3.33; Yellow streak; Resinous on crystal faces, pearly on cleavage surfaces luster; optically biaxial.
IMA symbol Apm, IMA status: approved, named in 2011.
A very low-temperature hydrothermal mineral.
It is found associated with Dufrénoysite, muscovite, orpiment, pyrite, realgar.
Alludes to the mineral’s triclinic (anorthic) symmetry and dimorphous relation to orpiment.