mineral
Weathered copper-bearing sulfide rock (likely bornite/chalcopyrite)
Bornite (Cu5FeS4) and/or chalcopyrite (CuFeS2), with oxidation tarnish
AI-generated identification · may be incorrectHardness about 3–4 Mohs; dark bronze to brassy metallic surface with iridescent blue-green, purple, and turquoise tarnish (“peacock ore”); massive, opaque, metallic luster, no obvious cleavage. Specific gravity commonly 4.1–4.3.
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Physical properties
Hardness about 3–4 Mohs; dark bronze to brassy metallic surface with iridescent blue-green, purple, and turquoise tarnish (“peacock ore”); massive, opaque, metallic luster, no obvious cleavage. Specific gravity commonly 4.1–4.3.
Formation & geological history
Forms in hydrothermal copper deposits and disseminated sulfide ores, typically in igneous-related veins; the colorful surface develops through oxidation and weathering over geological time.
Uses & applications
Copper ores are mined for electrical wiring, plumbing, alloys, and industrial use; attractive polished pieces are sold as mineral specimens, though many commercial “peacock ore” pieces are artificially treated.
Geological facts
True bornite is commonly called peacock ore, but chalcopyrite is frequently marketed under the same name and treated with acid to intensify colors.
Field identification & locations
Look for unusually high density, metallic sheen, brassy bronze beneath the tarnish, and a dark gray streak; copper-bearing sulfides may leave a sulfurous odor when freshly fractured. Common in Arizona, Montana, Peru, Chile, and other major copper districts.
