mineral

Bornite

Bornite (Cu5FeS4)

Hardness: 3 on Mohs scale; Color: Copper-red to brown on fresh surfaces, tarnishing to iridescent blues and purples; Luster: Metallic; Crystal Structure: Orthorhombic; Cleavage: Poor; Specific Gravity: 5.06-5.08

Hardness: 3 on Mohs scale
Luster: Metallic

Identified May 30, 2026More mineral →

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Physical properties

Formation & geological history

Formed in copper ore deposits, typically in hydrothermal veins, contact metamorphic zones, and as a secondary mineral in enriched zones of copper deposits.

Uses & applications

An important ore of copper (containing about 63% copper by mass); also popular as a display mineral for collectors due to its colors.

Geological facts

Commonly known as "Peacock Ore" because of its tarnish, which resembles the iridescent feathers of a peacock. While often confused with treated chalcopyrite, natural bornite produces a deep blue/purple tarnish.

Field identification & locations

Identify by its rapid tarnish from bronze to vibrant blue/purple. Found in copper mines worldwide, notably in Arizona-USA, Mexico, and Kazakhstan. Collectors should look for its metallic sheen and characteristic iridescence.