mineral

Bornite (Peacock Ore)

Bornite (Cu5FeS4)

Hardness: 3 on Mohs scale; Color: Bronze-brown but tarnishes to iridescent blue/purple/green; Luster: Metallic; Crystal structure: Orthorhombic; Cleavage: Poor; Specific gravity: 5.06-5.08

Hardness: 3 on Mohs scale
Color: Bronze-brown but tarnishes to iridescent blue/purple/green
Luster: Metallic

Identified May 9, 2026More mineral →

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Physical properties

Hardness: 3 on Mohs scale; Color: Bronze-brown but tarnishes to iridescent blue/purple/green; Luster: Metallic; Crystal structure: Orthorhombic; Cleavage: Poor; Specific gravity: 5.06-5.08

Formation & geological history

Forms primarily in hydrothermal veins and as a primary or secondary copper mineral in porphyry copper deposits. It is often found in contact metamorphic rocks and basic igneous rocks.

Uses & applications

Significant ore of copper; highly popular as a collector's specimen due to its vibrant 'peacock' iridescence.

Geological facts

Commonly known as 'Peacock Ore' because of its rainbow-like tarnish. While bornite naturally tarnishes, many samples sold in gift shops are actually chalcopyrite that has been acid-washed to force the iridescent oxidation.

Field identification & locations

Identify by its iridescent metallic tarnish and high copper content. Commonly found in copper mining districts like those in Chile, Arizona (USA), and Cornwall (UK). Submerging a suspect piece in dilute acid to see if it turns bright colors is a common test for artificial enhancement.