mineral

Bornite

Bornite (Cu5FeS4)

Hardness: 3 (Mohs), Color: Copper-red to brown on fresh surfaces, tarnishing to iridescent blue/purple; Luster: Metallic; Crystal Structure: Orthorhombic; Cleavage: Poor; Specific Gravity: 5.06-5.08

Luster: Metallic

Identified May 30, 2026More mineral →

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Physical properties

Hardness: 3 (Mohs), Color: Copper-red to brown on fresh surfaces, tarnishing to iridescent blue/purple; 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 or secondary copper mineral in sulfide deposits often associated with chalcopyrite and chalcocite.

Uses & applications

A significant ore of copper; highly valued as a collector specimen due to its vibrant iridescent tarnish.

Geological facts

Commonly known as Peacock Ore because of its brilliant iridescent tarnish. While it occurs naturally, many bright blue/purple industrial specimens sold are actually acid-treated chalcopyrite.

Field identification & locations

Identify by its iridescent metallic blue/purple tarnish over a copper-colored interior when freshly broken. Found frequently in Arizona (USA), Mexico, Peru, and Chile.