mineral
Gold-bearing pyrite-rich rock (iron pyrite)
Pyrite, FeS₂, likely in a quartz- or sulfide-rich matrix
AI-generated identification · may be incorrectBrassy yellow metallic luster with granular, flaky to massive texture; pyrite hardness 6–6.5 Mohs, cubic crystal structure, poor cleavage, and specific gravity about 5.0. The irregular dark matrix may include quartz, shale, or other sulfides; appearance alone cannot confirm native gold.
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Physical properties
Brassy yellow metallic luster with granular, flaky to massive texture; pyrite hardness 6–6.5 Mohs, cubic crystal structure, poor cleavage, and specific gravity about 5.0. The irregular dark matrix may include quartz, shale, or other sulfides; appearance alone cannot confirm native gold.
Formation & geological history
Typically forms hydrothermally in veins and replacement deposits, or diagenetically in sedimentary rocks, from geologically ancient systems ranging from Precambrian to Cenozoic. Gold may occur microscopically within pyrite, but visible gold is not established here.
Uses & applications
Pyrite is mined for sulfur, sulfuric-acid production, and sometimes gold recovery; attractive specimens are collected. It has little jewelry value because it tarnishes and can oxidize.
Geological facts
Often called “fool’s gold”; unlike gold, it is brittle, may form sharp cubes, and leaves a dark greenish-black streak rather than a yellow streak.
Field identification & locations
Look for cubic crystals, brittle fracture, and a dark streak; gold is softer, malleable, and leaves a yellow streak. Common in hydrothermal ore districts worldwide, including Spain, Peru, China, and the United States.
