Pyrite

Physical Properties

Hardness: 6-6.5 (Mohs), Color: Pale brass-yellow to silver-gold, Luster: Metallic, Crystal structure: Isometric (often cubes or pyritohedrons), Cleavage: Indistinct, Specific gravity: 4.9-5.2

Formation & Geological History

Formed in high and low-temperature hydrothermal veins, as an accessory mineral in igneous rocks, and in sedimentary rocks such as shale or coal through organic matter reduction.

Uses & Applications

Previously used for the production of sulfuric acid; currently used for ornamental pieces, jewelry (marcasite jewelry), and as a minor source of iron.

Geological Facts

Commonly known as Fool's Gold due to its resemblance to precious metals. It sparks when struck against steel, a property that led to its use in wheel-lock firearms during the 16th century.

Field Identification & Locations

Identify in the field by its brittle nature (gold is malleable), metallic luster, and blackish-green streak on a streak plate. Found globally, with notable deposits in Spain, Peru, and Russia.

Identified on: 4/20/2026

Mode: Standard