mineral

Bornite

Bornite (Cu5FeS4)

Hardness: 3 (Mohs scale); Color: Copper-red to bronze-brown on fresh surfaces, tarnishing to iridescent blues, purples, and greens; Luster: Metallic; Crystal Structure: Orthorhombic (often massive); Cleavage: Poor; Specific Gravity: 5.06-5.08.

Hardness: 3 (Mohs scale)
Luster: Metallic

Identified June 8, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hydrothermal veins, contact metamorphic zones, and as a secondary mineral in the enrichment zones of copper sulfide deposits. It often occurs alongside chalcopyrite and chalcocite.

Uses & applications

Major ore of copper. Specimens with high iridescence are popular for mineral collecting and display. Occasionally used as a decorative material in lapidary work.

Geological facts

Commonly known as 'Peacock Ore' due to the vibrant iridescent tarnish that resembles peacock feathers. While naturally iridescent, many specimens sold in gift shops are actually chalcopyrite that has been acid-enhanced to produce these colors.

Field identification & locations

Identify in the field by its metallic luster and the 'oil-slick' iridescent tarnish. It is much softer than chalcopyrite and can be scratched with a copper coin. Found commonly in Butte, Montana; Tsumeb, Namibia; and Cornwall, England.