mineral

Bornite

Copper Iron Sulfide (Cu5FeS4)

Hardness: 3-3.25 (Mohs scale), Color: Brownish-bronze (fresh), Iridescent purple/blue peacock colors (weathered), Luster: Metallic, Crystal structure: Orthorhombic, Cleavage: Poor, Specific gravity: 5.06-5.08

Hardness: 3-3

Identified June 17, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hydrothermal veins, contact metamorphic zones, and as a primary mineral in basic igneous rocks; found in sulfide deposits alongside chalcopyrite and chalcocite.

Uses & applications

Bornite is a significant ore of copper. High-quality specimens with intense iridescence are widely collected as "Peacock Ore" and used in decorative desk items or hobbyist mineral collections.

Geological facts

Commonly nicknamed 'peacock ore' because it tarnishes to iridescent shades of blue, purple, and green. This iridescence creates a natural rainbow effect once the surface is exposed to air and moisture.

Field identification & locations

Identify by its distinctive iridescent tarnish on a metallic surface. Often found in major copper mining regions like Montana, Arizona, and Cornwall, UK. It is softer than most metals and leaves a grayish-black streak.