mineral

Pyrite (fool’s gold)

Iron disulfide, FeS₂; usually cubic or pyritohedral crystals

AI-generated identification · may be incorrect

Brassy metallic gold color, metallic luster, opaque, Mohs hardness 6–6.5, specific gravity about 5.0; poor cleavage and commonly granular or cubic crystal structure. The specimen appears as a cluster of tarnished, intergrown crystals.

Identified August 30, 2026More mineral →

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Physical properties

Formation & geological history

Forms in hydrothermal veins, sedimentary rocks, coal beds, and metamorphic environments when iron and sulfur react under reducing conditions. It occurs from ancient Precambrian deposits to modern mineralizing systems.

Uses & applications

Used historically as a sulfur source and occasionally for sulfuric-acid production; attractive specimens are collected and sometimes used decoratively. It is not a durable jewelry gemstone because it can tarnish and oxidize.

Geological facts

Unlike gold, pyrite is brittle and typically produces a dark streak rather than a yellow-gold streak. Oxidation may create acidic runoff and iron-oxide coatings.

Field identification & locations

Common localities include Spain, Peru, Italy, China, Mexico, and the United States. Identify it by its brassy metallic appearance, high hardness, cubic forms, and brittle fracture; avoid prolonged moisture exposure.