mineral
Metallic sulfide mineral fragment, likely bornite or chalcopyrite
Bornite (Cu₅FeS₄) or chalcopyrite (CuFeS₂)
AI-generated identification · may be incorrectSmall 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.
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Physical properties
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.
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.
