Rock Identifier
Chalcopyrite (Chalcopyrite (CuFeS2)) — mineral
mineral

Chalcopyrite

Chalcopyrite (CuFeS2)

AI-generated identification · may be incorrect

Hardness: 3.5-4.0; Color: Brass yellow to golden-yellow, often with an iridescent purple/blue tarnish; Luster: Metallic; Crystal Structure: Tetragonal; Cleavage: Poor/Indistinct; Specific Gravity: 4.1 to 4.3; Streak: Greenish-black

Hardness
3
Luster
Metallic
Streak
Greenish-black
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Physical properties

Hardness: 3.5-4.0; Color: Brass yellow to golden-yellow, often with an iridescent purple/blue tarnish; Luster: Metallic; Crystal Structure: Tetragonal; Cleavage: Poor/Indistinct; Specific Gravity: 4.1 to 4.3; Streak: Greenish-black

Formation & geological history

Formed in primary sulfide deposits within hydrothermal veins, contact metamorphic environments, and through magmatic segregation. It occurs in various geological ages alongside other minerals like pyrite, bornite, and sphalerite.

Uses & applications

It is the world's most important ore of copper. It is also used in metallurgy for gold and silver extraction as a byproduct, and as a popular specimen for mineral collectors and educational purposes.

Geological facts

When chalcopyrite is treated with acid, it develops an intense iridescent tarnish, and in this state, it is frequently sold as 'Peacock Ore' or 'Bornite', though true bornite is a distinct mineral species. It has been used for copper extraction since the Bronze Age.

Field identification & locations

Identify in the field by its brassy yellow color that is more yellow than pyrite and softer than a steel knife (pyrite is harder than steel). It is commonly found in copper mines worldwide, including the southwestern USA, Chile, and Canada. Collectors should look for its distinctive greenish-black streak when scratched on a porcelain plate.

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