4.1" Galena, Chalcopyrite, Quartz and Orpiment Association - Palomo Mine

Quartz is the name given to silicon dioxide (SiO2) and is the second most abundant mineral in the Earth's crust. Quartz crystals generally grow in silica-rich environments--usually igneous rocks or hydrothermal environments like geothermal waters--at temperatures between 100°C and 450°C, and usually under very high pressure. In either case, crystals will precipitate as temperatures cool, just as ice gradually forms when water freezes. Quartz veins are formed when open fissures are filled with hot water during the closing stages of mountain formation: these veins can be hundreds of millions of years old.

Orpiment is a bright orange to yellow arsenic sulfide mineral. Its name is derived from the latin phrase auripigmentum, meaning “gold pigment”. It is frequently found as a decay byproduct and in association with another arsenic mineral, realgar. Orpiment crystals are commonly found in dense groupings containing small, prismatic crystals, often with chisel-shaped or triangular pyramidal terminations.

Orpiment contains a significant amount of the poisonous mineral arsenic. While it’s not going to pose a health hazard sitting on a shelf, it’s recommended that you wash your hands after handling it.