Bornite Value, Price, and Jewelry Information

BORNITE: Butte, Montana, (specimens 2 inches across). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Bornite

Bornite is suitable only for cabochons. The bronzy color rapidly tarnishes in air to a magnificent iridescent color display, mostly purple, but also with blue and green tones. Bornite is too soft and brittle for anything but a collector curiosity, although cabochons are quite attractive when they tarnish. The material is not rare, so cabochons have no great value beyond the effort of cutting.

Bornite Information

Data Value
Name Bornite
Stone Sizes Cabochons could be very large, several inches long, because the massive material fromore veins are available in large pieces.
Formula Cu5FeS4
Colors Copper red to bronze. Tarnishes to an iridescent purple color.
Fracture Uneven to conchoidal
Hardness 3
Cleavage Poor, indistinct. In traces on {111}
Crystallography Orthorhombic. Crystals rare, twinned; usually massive, compact.
Luster Metallic.
Specific Gravity 5.08
Transparency Opaque.

STREAK: Light grayish black.

OCCURRENCE: Low temperature copper deposits.

Bristol, Connecticut; Virginia; North Carolina; Montana; Arizona; Colorado; California

Canada; Chile; Peru; England; Italy; Germany; South Africa; Madagascar.

COMMENTS: Bornite is suitable only for cabochons. The bronzy color rapidly tarnishes in air to a magnificent iridescent color display, mostly purple, but also with blue and green tones. Bornite is too soft and brittle for anything but a collector curiosity, although cabochons are quite attractive when they tarnish. The material is not rare, so cabochons have no great value beyond the effort of cutting.

NAME:  After Ignatius von Born, eighteenth-century mineralogist.

 

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