mineral

Bornite

Bornite (Cu5FeS4)

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale); Color: Brownish-bronze turning to iridescent blue-purple-pink (peacock colors) upon tarnishing; Luster: Metallic; Crystal system: Orthorhombic; Specific Gravity: 5.06-5.08.

Hardness: 3 (Mohs scale)
Luster: Metallic

Identified April 3, 2026More mineral →

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Physical properties

Hardness: 3 (Mohs scale); Color: Brownish-bronze turning to iridescent blue-purple-pink (peacock colors) upon tarnishing; Luster: Metallic; Crystal system: Orthorhombic; Specific Gravity: 5.06-5.08.

Formation & geological history

Formed in hydrothermal veins, contact metamorphic zones, and in the enriched zones of copper sulfide deposits. It can be found in igneous and metamorphic rocks.

Uses & applications

A significant ore of copper. High-quality specimens are highly valued by mineral collectors for their vibrant 'peacock' tarnish.

Geological facts

Commonly known as 'Peacock Ore' because of the vivid iridescent tarnish that develops on its surface when exposed to air. Authentic bornite tarnishes naturally, though some commercial pieces sold as 'peacock ore' are actually chalcopyrite treated with acid.

Field identification & locations

Identified by its distinctive metallic iridescent 'oil slick' colors on a dark metallic base. It has a grayish-black streak. Common locations include Montana (USA), Cornwall (UK), and Kazakhstan.