mineral

Bornite

Bornite (Cu5FeS4)

Hardness: 3-3.25; Color: Brownish-bronze turning to iridescent purple, blue, and green on tarnish; Luster: Metallic; Crystal: Orthorhombic; Cleavage: Poor; Specific Gravity: 5.06-5.08

Hardness: 3-3
Luster: Metallic

Identified May 9, 2026More mineral →

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Physical properties

Hardness: 3-3.25; Color: Brownish-bronze turning to iridescent purple, blue, and green on tarnish; Luster: Metallic; Crystal: Orthorhombic; Cleavage: Poor; Specific Gravity: 5.06-5.08

Formation & geological history

Forms in copper ore deposits through hydrothermal alteration of primary sulfides. It is often found in contact metamorphic zones, igneous rocks, and sedimentary copper shales.

Uses & applications

A major ore mineral of copper due to its high copper content (approximately 63%); also a popular and colorful mineral specimen for collectors.

Geological facts

Commonly nicknamed 'Peacock Ore' due to the vibrant iridescent tarnish that resembles peacock feathers. While naturally iridescent, many commercial 'Peacock Ore' specimens are actually Chalcopyrite treated with acid.

Field identification & locations

Look for the distinct iridescent 'oil-slick' colors on a metallic surface. Often found alongside minerals like Chalcopyrite, Quartz, and Malachite in mining districts of Arizona, Montana, Mexico, and Chile.