mineral
Copper-bearing sulfide ore, possibly bornite/chalcopyrite
Likely bornite (Cu5FeS4) and/or chalcopyrite (CuFeS2) in a sulfide-rich host rock
AI-generated identification · may be incorrectBrassy metallic to iridescent blue-purple and coppery surfaces suggest tarnished copper sulfides; hardness about 3–4 Mohs, opaque, with uneven fracture and high specific gravity. Identification is provisional from the photograph.
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Physical properties
Brassy metallic to iridescent blue-purple and coppery surfaces suggest tarnished copper sulfides; hardness about 3–4 Mohs, opaque, with uneven fracture and high specific gravity. Identification is provisional from the photograph.
Formation & geological history
Forms in hydrothermal veins and magmatic-hydrothermal ore deposits when hot, sulfur-rich fluids precipitate copper and iron sulfides; commonly associated with quartz, pyrite, and altered igneous rocks. Ages vary widely by deposit.
Uses & applications
Important copper ore for electrical wiring, plumbing, alloys, and industrial equipment; attractive iridescent pieces are collected, though this specimen appears rough and low grade.
Geological facts
Bornite is nicknamed “peacock ore” after oxidation produces vivid blue, purple, and green tarnish. Fresh bornite is typically copper-red to bronze, while chalcopyrite is brassy yellow.
Field identification & locations
Look for metallic luster, unusual heft, brassy or coppery color, and blue-purple tarnish; a streak, hardness, and chemical test or X-ray diffraction are needed for confirmation. Common localities include Arizona, Montana, Peru, Chile, and Cornwall.
