metamorphic
Pyrite-bearing metamorphic rock (probable schist or quartzite)
Quartz–mica schist with disseminated pyrite; approximate composition SiO₂ + phyllosilicates + FeS₂
AI-generated identification · may be incorrectGray, fine- to medium-grained, weakly sparkly surface with brassy-yellow metallic flecks; likely Mohs 2–7 overall, pyrite 6–6.5, quartz 7. Luster is primarily submetallic to earthy, with no obvious cleavage visible in the specimen.
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Physical properties
Gray, fine- to medium-grained, weakly sparkly surface with brassy-yellow metallic flecks; likely Mohs 2–7 overall, pyrite 6–6.5, quartz 7. Luster is primarily submetallic to earthy, with no obvious cleavage visible in the specimen.
Formation & geological history
Likely formed when clay-rich sediment or quartz-rich rock was buried, heated, and compressed, with later hydrothermal or metamorphic fluids depositing pyrite. Its exact geological age cannot be determined from the photograph.
Uses & applications
Usually a collector specimen or field sample; pyrite may be studied for mineral exploration, while schist and quartzite can serve locally as aggregate or decorative stone.
Geological facts
The brassy grains are probably pyrite (“fool’s gold”), though chalcopyrite is another possibility. A fresh streak test and hardness testing help distinguish them.
Field identification & locations
Common in metamorphic belts and hydrothermal zones worldwide, including the Appalachians, Andes, Alps, and Precambrian shields. Look for foliation, quartz-rich layers, and metallic grains; pyrite streak is dark greenish-black, unlike gold’s yellow streak.
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