Orpiment
Image: Robert M. Lavinsky (CC BY-SA 3.0)
Mineral NameOrpiment
Chemical FormulaAs₂S₃
Mohs Hardness1.5
Crystal Systemmonoclinic
Lusterresinous
Streak Colorpale yellow
Cleavageperfect on {010}
Fractureconchoidal
Specific Gravity3.49
Colorslemon yellow, golden yellow, orange yellow, brownish yellow
Transparencytranslucent
Type LocalityEl'brusskiy (Elbrusskii) Arsenic mine, Elbrus, Kabardino-Balkarian Republic, Northern Caucasus, Russia
Mineral GroupSulfides
Usespigment (historical), collector
Associated Mineralsbaryte, realgar, arsenic, calcite, gypsum
Rarityuncommon
Description
This specimen displays bright, vibrant lemon-yellow to orange-yellow foliated masses of orpiment, often with a resinous to pearly luster, sometimes forming tabular crystals.
Geological Context
Orpiment is a low-temperature hydrothermal mineral, typically found in hot spring deposits, volcanic fumaroles, and as an alteration product of other arsenic minerals like realgar in ore veins.
