mineral
Bornite
Bornite (Cu5FeS4)
Hardness: 3 (Mohs scale), Color: Brownish-bronze (tarnishes to iridescent purple/blue), Luster: Metallic, Crystal system: Orthorhombic (often massive), Cleavage: Poor, Specific Gravity: 5.06-5.08
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Physical properties
Hardness: 3 (Mohs scale), Color: Brownish-bronze (tarnishes to iridescent purple/blue), Luster: Metallic, Crystal system: Orthorhombic (often massive), Cleavage: Poor, Specific Gravity: 5.06-5.08
Formation & geological history
Forms in copper ore deposits, specifically in hydrothermal veins, contact metamorphic zones, and as a secondary mineral in enriched zones. Often found alongside chalcopyrite.
Uses & applications
Significant ore of copper; highly sought after by collectors for its peacock-like iridescent tarnish.
Geological facts
Commonly nicknamed 'peacock ore' due to its colorful iridescent tarnish. While naturally occurring, many specimens in tourist shops are actually chalcopyrite treated with acid to enhance colors; this natural-looking specimen shows the classic bornite patina.
Field identification & locations
Identify by its iridescent 'oil-slick' tarnish and gray-black streak. The location near Palermo, Sicily, aligns with historical mining and geological diversity in the Mediterranean copper-bearing belts.
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