Cobaltite
Image: Robert M. Lavinsky (CC BY-SA 3.0)
Mineral NameCobaltite
Chemical FormulaCoAsS
Mohs Hardness5.5
Crystal Systemorthorhombic
Lustermetallic
Streak Colorgreyish black
Cleavagegood on {100}
Fractureuneven
Specific Gravity6.3
Colorssilvery white, steel-gray, reddish tinge
Transparencyopaque
Type LocalityEspanola, Foster Township, Sudbury District, Ontario, Canada
Mineral Groupsulfides
Usesore of cobalt, collector's specimens
Associated Mineralsarsenopyrite, chalcopyrite, pyrite, calcite, quartz
Rarityrare
Description
This specimen features excellent, rare, silvery-white to slightly golden metallic cubic cobaltite crystals embedded in a dark matrix, characteristic of finds from the Sudbury District.
Geological Context
Cobaltite typically forms in high-temperature hydrothermal veins, contact metamorphic deposits, and sometimes in pegmatites, often associated with other cobalt-nickel-iron sulfides and arsenides.
