Pyrite is a common iron sulfide mineral (FeS2). It’s nickname is “fool's gold”. Pyrite has a metallic luster, brassy gold color (in contrast to the deep rich yellow gold color of true gold), dark gray to black streak, is hard (H=6 to 6.5), has no cleavage, and is moderately heavy for its size. It often forms cubic crystals or pyritohedrons (crystals having pentagonal faces).
Pyrite is common in many hydrothermal veins, shales, coals, and several types of metamorphic rocks.
Pyrite (5.8 cm across)
Pyrite concretion from an Upper Devonian black shale succession in Ross County, south-central Ohio, USA (Wayne State University collection, Detroit, Michigan, USA).