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Formula: As2S3
Valence: As3+2S2-3
Simple sulphide of arsenic, triclinic
paramorph of monoclinic
orpiment
Crystal System: Triclinic
Specific gravity: 3.33 measured, 3.321 calculated
Hardness: 1½:
Streak: Yellow
Colour: Greenish yellow
Solubility: Insoluble in concentrated hydrochloric acid
Environments
Localities
At the type locality, the Palomo mines, Santa Ana District, Castrovirreyna Province, Huancavelica, Peru,
anorpiment occurs as a low-temperature hydrothermal mineral associated with
dufrénoysite, muscovite,
orpiment, pyrite and
realgar. It occurs in drusy crusts of wedge-shaped, transparent, greenish
yellow crystals. The streak is yellow. The lustre is resinous on crystal faces, but pearly on cleavage surfaces. The
mineral is sectile with an irregular fracture and one perfect and easy cleavage
(MM 75.6.2857–2867).
Anorpiment from the Palomo Mines - Image
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