Rock Identifier
Peacock Ore (Bornite or Chalcopyrite) (Bornite (Cu₅FeS₄) or iridescent Chalcopyrite (CuFeS₂)) — mineral
mineral

Peacock Ore (Bornite or Chalcopyrite)

Bornite (Cu₅FeS₄) or iridescent Chalcopyrite (CuFeS₂)

Hardness: 3-3.5 (Bornite) or 3.5-4 (Chalcopyrite). Color: Brass-yellow or copper-red on fresh surfaces; tarnishes to brilliant blues, purples, and magentas. Luster: Metallic. Crystal structure: Orthorhombic or tetragonal. Specific gravity: 4.9–5.3.

Hardness
3-3
Color
Brass-yellow or copper-red on fresh surfaces
Luster
Metallic
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Physical properties

Hardness: 3-3.5 (Bornite) or 3.5-4 (Chalcopyrite). Color: Brass-yellow or copper-red on fresh surfaces; tarnishes to brilliant blues, purples, and magentas. Luster: Metallic. Crystal structure: Orthorhombic or tetragonal. Specific gravity: 4.9–5.3.

Formation & geological history

Formed in hydrothermal veins and porphyry copper deposits. It often occurs alongside other sulfide minerals like pyrite and galena. The iridescent 'peacock' effect is caused by a thin film of oxidized copper that develops after exposure to air.

Uses & applications

Bornite is an important ore of copper. In its iridescent form, it is widely popular as a decorative specimen for collectors, in jewelry, and for metaphysical purposes.

Geological facts

Peacock Ore is often actually Chalcopyrite that has been acid-washed (typically with vinegar or hydrochloric acid) to produce its characteristic vibrant colors artificially. Genuine Bornite develops this tarnish naturally, but much more slowly.

Field identification & locations

Identify in the field by its intense 'oil slick' iridescent tarnish and metallic weight. It can be distinguished from gold by its brittleness and tendency to crumble. Common locations include Mexico, Arizona (USA), and Chile.

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