Pyrite

Physical Properties

Hardness: 6-6.5 on Mohs scale. Color: Pale brass-yellow. Luster: Metallic. Crystal structure: Isometric (cubic). Cleavage: Poor/Indistinct. Specific gravity: 4.9-5.2.

Formation & Geological History

Formed in high and low temperature hydrothermal veins, by magmatic segregation, and as an accessory mineral in igneous and metamorphic rocks. It also forms in sedimentary rocks via bacterial reduction of sulfates.

Uses & Applications

Primary source of sulfur and sulfuric acid. Used historically in firearms (wheellocks), as secondary iron ore, and commonly in jewelry (as marcasite) and as collector specimens.

Geological Facts

Also known as Fool's Gold because its color resembles real gold, though it is much harder and more brittle. It is the most common sulfide mineral on Earth.

Field Identification & Locations

Identified by its brassy color, cubic crystal habit, and green-black streak on a porcelain plate. Common locations include Peru, Spain, Italy, and various sites across the United States.

Identified on: 4/21/2026

Mode: Standard