mineral

Metallic sulfide mineral fragment, likely bornite or chalcopyrite

Bornite (Cu₅FeS₄) or chalcopyrite (CuFeS₂)

AI-generated identification · may be incorrect

Small irregular metallic fragment with copper-purple/iridescent tarnish; likely Mohs 3–4, opaque, metallic luster, and poor cleavage. The image is insufficient for confident distinction from tarnished chalcopyrite or another copper sulfide.

Identified August 9, 2026More mineral →

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Physical properties

Formation & geological history

Forms in hydrothermal copper deposits, often with quartz and other sulfides, through cooling mineral-rich fluids; deposits range from Precambrian to geologically recent. The vivid purple-blue surface is commonly a weathering or oxidation film (“peacock ore”).

Uses & applications

Copper sulfides are important copper ores; attractive pieces are sold as inexpensive mineral specimens, though many “peacock ore” pieces are artificially acid-treated.

Geological facts

Bornite is nicknamed peacock ore for its iridescent tarnish, while untreated bornite is commonly bronze-brown. Chalcopyrite is typically brassy yellow before tarnishing.

Field identification & locations

Check for metallic heft, opacity, and a dark streak; a copper-bearing specimen may react with nitric acid, but testing can damage it. Common localities include Arizona, Montana, Peru, Mexico, and Cornwall.