mineral
Pyrite-bearing quartz rock
Pyrite (FeS₂) in quartz-rich matrix, possibly with mica or chlorite
AI-generated identification · may be incorrectHardness: pyrite 6–6.5 Mohs; quartz 7. Metallic brass-yellow to gray-black reflective grains occur in a pale translucent matrix. Pyrite is cubic or granular, has no cleavage and a dark greenish-black streak; the specimen appears irregular and naturally rough.
- Hardness
- pyrite 6–6
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Physical properties
Hardness: pyrite 6–6.5 Mohs; quartz 7. Metallic brass-yellow to gray-black reflective grains occur in a pale translucent matrix. Pyrite is cubic or granular, has no cleavage and a dark greenish-black streak; the specimen appears irregular and naturally rough.
Formation & geological history
Likely a hydrothermal quartz vein or metamorphic sulfide assemblage formed when mineral-rich fluids deposited pyrite in fractures, commonly during the Paleozoic–Mesozoic or older depending on locality. Exact age and origin require locality data or testing.
Uses & applications
Collected as a sulfide specimen and sometimes used as an ore of iron and sulfur; pyrite is not generally used as a gemstone because it tarnishes and is brittle. Quartz-rich pieces have modest decorative value.
Geological facts
Pyrite is commonly called “fool’s gold,” but its silvery-brassy metallic luster and darker streak distinguish it from native gold. Oxidation can produce rusty iron-oxide coatings and acidic drainage.
Field identification & locations
Look for metallic brassy grains, high apparent density, and a dark streak; a steel scratch test should not easily scratch pyrite, while quartz scratches glass. Common sources include Peru, Spain, Italy, China, and hydrothermal districts worldwide.
