mineral

Bornite

Cu5FeS4

Hardness: 3 on the Mohs scale. Color: Bronze to copper-red on fresh surfaces, rapidly tarnishing to iridescent purple, blue, and green peacock colors. Luster: Metallic. Crystal Structure: Orthorhombic. Cleavage: Poor, conchoidal to uneven fracture. Specific Gravity: 4.9 - 5.3.

Hardness: 3 on the Mohs scale
Luster: Metallic

Identified August 3, 2026More mineral →

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Physical properties

Formation & geological history

Forms typically in hydrothermal veins, contact metamorphic zones, and in the secondary enrichment zones of copper ore deposits alongside other copper minerals like chalcopyrite and chalcocite.

Uses & applications

A major ore of copper used in industrial metal production, and highly sought after by mineral collectors for its striking iridescent tarnish.

Geological facts

Commonly known as 'peacock ore' due to its vibrant, multi-colored iridescent tarnish that develops when exposed to air. Natural bornite usually tarnishes rather quickly, though some brightly colored specimens sold commercially are treated with acid to enhance the iridescence.

Field identification & locations

Identified easily by its distinctive metallic luster, soft copper-red fresh color, and characteristically rapid iridescent purple and blue tarnish. Found worldwide, with notable deposits in the USA, Mexico, Chile, and England.