mineral

Bornite (Peacock Ore)

Bornite (Cu5FeS4)

Hardness: 3 (Mohs scale), Color: Brownish-red (tarnishes to iridescent purple, blue, and green), Luster: Metallic, Crystal system: Orthorhombic, Cleavage: Poor, Specific Gravity: 5.06-5.08

Identified May 9, 2026More mineral →

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Physical properties

Hardness: 3 (Mohs scale), Color: Brownish-red (tarnishes to iridescent purple, blue, and green), Luster: Metallic, Crystal system: Orthorhombic, Cleavage: Poor, Specific Gravity: 5.06-5.08

Formation & geological history

Formed primarily in hypothermal and mesothermal copper-bearing veins, as well as in contact metamorphic zones and porphyry copper deposits. It results from the crystallization of hydrothermal fluids.

Uses & applications

A major ore of copper; highly valued as a collector's specimen due to its vibrant iridescent tarnish; occasionally used in decorative items and jewelry.

Geological facts

Often called 'Peacock Ore' due to the brilliant iridescent colors that occur when the surface is exposed to air and oxidizes. While it occurs naturally, some commercially sold 'peacock ore' is actually chalcopyrite that has been acid-washed to induce tarnish.

Field identification & locations

Identified by its distinctive iridescent 'oil-slick' colors over a metallic surface and relatively low hardness (can be scratched with a copper coin). Commonly found in Arizona (USA), Kazakhstan, and Chile.