Bournonite
Image: Andrew Silver (Public domain)
Mineral NameBournonite
Chemical FormulaPbCuSbS₃
Mohs Hardness2.5
Crystal Systemorthorhombic
Lustermetallic
Streak Colorblackish-gray
Cleavagedistinct on {010}, less distinct on {001} and {110}
Fractureconchoidal to uneven
Specific Gravity5.8
Colorssteel-gray, iron-black, lead-gray
Transparencyopaque
Type LocalityPříbram (Czech Republic), Neudorf (Germany), Cornwall (England), Huaron (Peru)
Mineral GroupSulfosalts
Usesminor ore of lead, copper, and antimony, collector
Associated Mineralsgalena, sphalerite, tetrahedrite, chalcopyrite, pyrite, quartz
Rarityuncommon
Description
This specimen displays dark, metallic, blocky crystals of Bournonite, likely exhibiting its characteristic 'cogwheel' twinning, with a pen for scale.
Geological Context
Bournonite typically forms in hydrothermal veins at low to moderate temperatures, often found in lead-zinc-silver deposits associated with other sulfide minerals.
