Tennantite
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY 3.0)
Mineral NameTennantite
Chemical Formula(Cu,Fe)12As4S13
Mohs Hardness3.5
Crystal Systemcubic
Lustermetallic
Streak Colorblack to brownish-black
Cleavageindistinct/poor
Fractureconchoidal to uneven
Specific Gravity4.85
Colorssteel-gray, iron-black, lead-gray, greenish-black
Transparencyopaque
Type LocalityTsumeb Mine, Oshikoto Region, Namibia
Mineral GroupSulfosalts
Usesore of copper, ore of arsenic, collector
Associated Mineralschalcopyrite, pyrite, sphalerite, galena, quartz, calcite, barite
Rarityuncommon
Description
This specimen displays dark, blocky, pseudo-octahedral crystals of tennantite with a metallic luster. Some areas show a greenish tarnish, and small, light-colored associated crystals are present.
Geological Context
Tennantite typically forms in hydrothermal veins, contact metamorphic deposits, and volcanogenic massive sulfide deposits. It is often found in complex polymetallic ore deposits alongside other sulfides of copper, lead, and zinc.
