Pyrite with Calcite & Quartz

Pyrite with Calcite and Quartz from the Huarón Mine, Pasco, Peru, measuring 40 × 40 × 27 mm and weighing 50 grams. A good solid sulfide specimen from one of the classic silver-lead-zinc districts of the Peruvian Andes.

Pyrite is iron disulfide, FeS2, isometric, and its bright brassy, often striated cubic crystals make it one of the most immediately recognisable sulfides in any collection. The Huarón district's polymetallic veins, part of the wider mineralised belt around Cerro de Pasco in the Peruvian Andes, deposited Pyrite alongside Quartz as gangue, with Calcite typically forming later, filling whatever open space remained once the main phase of sulfide mineralisation had finished.

Huarón has been one of Peru's significant producing mines for decades, and a specimen like this, naming all three of its principal minerals together, gives a fuller picture of a working Andean vein system than any single species could on its own. This piece is from the Alan Waldon Collection.