mineral

Chalcopyrite

Chalcopyrite (CuFeS2)

Hardness: 3.5-4 (Mohs scale); Color: Brass yellow to golden, often with iridescent blue/purple tarnish (peacock ore); Luster: Metallic; Crystal Structure: Tetragonal; Cleavage: Indistinct; Specific Gravity: 4.1-4.3

Hardness: 3
Luster: Metallic

Identified March 20, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily in hydrothermal veins from high-temperature copper-bearing fluids. It is also found in igneous rocks through magmatic segregation and in metamorphic rocks via contact metamorphism. Its geological age spans from the Archean to the present.

Uses & applications

The primary and most important ore of copper. It is used extensively in industry for electrical wiring, plumbing, and electronics. Iridescent specimens known as 'Peacock Ore' are popular in the gem and mineral collecting trade.

Geological facts

Commonly confused with gold, it is often called 'Fool's Gold' (though this title is more frequently associated with pyrite). However, chalcopyrite is softer than pyrite and can be scratched with a knife. It becomes iridescent due to surface oxidation.

Field identification & locations

Identify in the field by its brassy yellow color, greenish-black streak, and the fact that it is soft enough to be scratched by a steel nail. Common locations include high-temperature ore deposits in Arizona (USA), Cornwall (UK), and mountainous regions of Chile and Peru.