mineral

Pyrite (“fool’s gold”)

Iron disulfide, FeS₂; likely a pyrite-rich sulfide specimen

AI-generated identification · may be incorrect

Brassy yellow metallic luster with blocky, granular crystals; Mohs hardness 6–6.5, cubic crystal system, poor cleavage, and specific gravity about 5.0. The appearance is consistent with pyrite, though image-only identification cannot exclude marcasite or chalcopyrite.

Identified September 1, 2026More mineral →

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Physical properties

Formation & geological history

Forms in hydrothermal veins, sedimentary rocks, and metamorphic environments when sulfur-rich fluids react with iron-bearing minerals. Pyrite occurs from Precambrian rocks to modern deposits and has no single geological age.

Uses & applications

Collected as a mineral specimen and formerly used as a sulfur and iron source; historically important in sulfuric-acid production. Attractive crystals are inexpensive display pieces, but pyrite is generally unsuitable for jewelry because it tarnishes and can oxidize.

Geological facts

Its metallic gold color led to the name “fool’s gold,” but its higher hardness and lack of malleability distinguish it from native gold. Oxidation can produce acidic, sulfate-rich runoff and powdery surface decay.

Field identification & locations

Look for brassy color, metallic luster, heavy feel, and cubic or pyritohedral crystal faces; a streak test gives a greenish-black to brown-black streak, unlike gold’s yellow streak. Common localities include Peru, Spain, Italy, the United States, China, and Morocco.