Peacock Ore (Chalcopyrite)

Physical Properties

Hardness: 3.5-4.0 Mohs; Color: Brass yellow (tarnishes to iridescent blue, purple, and green); Luster: Metallic; Crystal Structure: Tetragonal; Cleavage: Poor/Indistinct; Specific Gravity: 4.1-4.3

Formation & Geological History

Formed primarily in hydrothermal veins from hot metal-rich fluids, often associated with igneous intrusions; also found in contact metamorphic rocks and some sedimentary copper deposits.

Uses & Applications

Major ore of copper. In specimen form, it is widely used in jewelry (as pendants), crystal healing, and as a popular starter mineral for collectors.

Geological Facts

Natural peacock tarnish occurs due to oxidation, but many vivid blue/purple specimens sold in shops are actually chalcopyrite that has been acid-washed (typically with vinegar or citric acid) to accelerate the iridescence.

Field Identification & Locations

Identify by its metallic luster and intense rainbow tarnish (distinguishing it from Bornite which is darker). Found globally in copper mines like those in Chile, Arizona (USA), and Cornwall (UK).

Identified on: 4/23/2026

Mode: Standard