mineral

Bornite (Peacock Ore)

Bornite (Cu5FeS4)

Hardness: 3 on Mohs scale; Color: Brownish-bronze, tarnishing to iridescent purple/blue/green; Luster: Metallic; Crystal Structure: Orthorhombic; Cleavage: Poor; Specific Gravity: 5.06-5.08

Hardness: 3 on Mohs scale
Color: Brownish-bronze, tarnishing to iridescent purple/blue/green
Luster: Metallic

Identified May 3, 2026More mineral →

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Physical properties

Hardness: 3 on Mohs scale; Color: Brownish-bronze, tarnishing to iridescent purple/blue/green; Luster: Metallic; Crystal Structure: Orthorhombic; Cleavage: Poor; Specific Gravity: 5.06-5.08

Formation & geological history

Formed in hydrothermal veins, contact metamorphic zones, and as a primary mineral in copper deposits. It is often found in the supergene enrichment zone of copper ore bodies.

Uses & applications

Important ore of copper; highly popular as a decorative specimen for collectors and teaching tools in geology.

Geological facts

Often called 'Peacock Ore' because its iridescent tarnish resembles a peacock's feathers. While true Bornite naturally tarnishes, sometimes Chalcopyrite is treated with acid to mimic this effect.

Field identification & locations

Identified by its distinctive purple-blue tarnish, low hardness (can be scratched by a copper coin), and dark gray-black streak. Common in copper mines in Arizona and Montana (USA), Cornwall (UK), and Chile.