mineral

Pyrite (“fool’s gold”)

Pyrite, iron disulfide (FeS₂), commonly forming cubic crystals

AI-generated identification · may be incorrect

Brassy yellow metallic luster; Mohs hardness 6–6.5; opaque, dense (specific gravity ~5.0); commonly cubic, pyritohedral, or granular, with poor cleavage and uneven-to-conchoidal fracture.

Identified September 19, 2026More mineral →

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Physical properties

Brassy yellow metallic luster; Mohs hardness 6–6.5; opaque, dense (specific gravity ~5.0); commonly cubic, pyritohedral, or granular, with poor cleavage and uneven-to-conchoidal fracture.

Formation & geological history

Forms in hydrothermal veins and sedimentary environments, especially carbon-rich shales and limestones, through sulfide mineral precipitation. Specimen age depends on locality and may range from Paleozoic to recent hydrothermal formation.

Uses & applications

Used historically as a sulfur and sulfuric-acid source, and occasionally for decorative specimens, jewelry, and educational collections; it has little gemstone value because it can tarnish and weather.

Geological facts

Its metallic appearance resembles gold, but pyrite is harder and more brittle. It may oxidize in humid conditions to produce iron sulfates and sulfuric acid (“pyrite disease”).

Field identification & locations

Identify by brassy color, cubic crystal faces, high density, and a dark greenish-black streak; gold is softer, malleable, and leaves a yellow streak. Common localities include Peru, Spain, Italy, China, and the United States.