mineral
Peacock ore (iridescent bornite/chalcopyrite)
Bornite (Cu₅FeS₄), commonly sold as heat-treated chalcopyrite (CuFeS₂)
AI-generated identification · may be incorrectMetallic luster with purple, blue, green, and gold tarnish; opaque and typically massive rather than visibly crystalline. Hardness is about 3–3.5 for bornite and 3.5–4 for chalcopyrite; cleavage is poor, with specific gravity roughly 4.1–4.3.
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Physical properties
Metallic luster with purple, blue, green, and gold tarnish; opaque and typically massive rather than visibly crystalline. Hardness is about 3–3.5 for bornite and 3.5–4 for chalcopyrite; cleavage is poor, with specific gravity roughly 4.1–4.3.
Formation & geological history
A copper-iron sulfide formed in hydrothermal ore deposits and magmatic-hydrothermal systems, commonly associated with chalcopyrite, pyrite, and quartz. The vivid rainbow surface is usually an artificial oxidation treatment, not the natural appearance.
Uses & applications
Collected as a colorful mineral specimen and sometimes used decoratively; untreated material is a copper ore, though specimens have little industrial value.
Geological facts
The nickname “peacock ore” covers both naturally iridescent bornite and commonly treated chalcopyrite. The colors result from thin-film oxidation layers on the sulfide surface.
Field identification & locations
Identify by its heavy feel, metallic surface, brassy interior, and rainbow tarnish; a streak test is dark gray to black. Common localities include Cornwall, England; Butte, Montana; Peru; Mexico; and Arizona.
