Bornite
Image: <a href="//commons.wikimedia.org/wiki/User:Islam90" title="User:Islam90">Islam90</a> (CC BY-SA 4.0)
Mineral NameBornite
Chemical FormulaCu₅FeS₄
Mohs Hardness3
Crystal Systemorthorhombic
Lustermetallic
Streak Colorgreyish black
Cleavageindistinct/poor on {111}
Fractureconchoidal
Specific Gravity5
Colorscopper-red, brownish bronze, iridescent blue, purple, red, black
Transparencyopaque
Type LocalityButte, Montana, USA; Cornwall, England; Mexico; Chile
Mineral GroupSulfides
Usescopper ore, collector
Associated Mineralschalcopyrite, pyrite, covellite, chalcocite, enargite
Raritycommon
Description
The image displays a polished section of bornite under a petrographic microscope, showing a bright yellowish-gold, vein-like mineral within a lighter, scratched matrix, alongside darker greyish-green inclusions. In hand specimen, bornite is characterized by its rapid tarnishing to iridescent blue, purple, and red hues, earning it the nickname 'peacock ore'.
Geological Context
Bornite is a significant primary copper ore mineral typically found in hydrothermal veins, porphyry copper deposits, and contact metamorphic deposits. It forms under moderate to high temperatures, often in association with other copper sulfides.
