mineral

Chalcopyrite (Peacock Ore)

Chalcopyrite (CuFeS2)

Hardness: 3.5-4 (Mohs); Color: Brassy yellow naturally, but often exhibits colorful iridescent tarnish (purple, blue, green, gold); Luster: Metallic; Crystal Structure: Tetragonal; Cleavage: Poor; Specific Gravity: 4.1-4.3

Hardness: 3
Luster: Metallic

Identified July 20, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hydrothermal veins, contact metamorphic deposits, and as a primary mineral in igneous rocks. When the surface oxidizes, it creates the characteristic iridescent tarnish known as bornite or peacock ore coating.

Uses & applications

The most important ore of copper; also used as a decorative specimen for collectors and occasionally in metaphysical jewelry.

Geological facts

While often confused with gold, it is more brittle and has a lower hardness. The iridescent effect is most commonly produced or enhanced by acid washing the mineral in a laboratory to display the range of colors seen here.

Field identification & locations

Identified by its metallic luster, brassy base color (where fresh), and greenish-black streak. Commonly found in copper mines worldwide, particularly in Arizona, Chile, and Cornwall. Collectors should look for vibrant multi-colored oxidation layers.