IMA Abbreviation (Whitney-Evans 2010)
Cob
→ Cobaltite
Co-As sulfide
Standard symbol from American Mineralogist (Whitney & Evans, 2010). Used in thin-section labeling, phase diagrams, and IMA-style species records.
Mohs 5.5
Vickers (~) 540 HV
Knoop (~) 620 HK
Geological setting
Hydrothermal
Element composition by mass
Formula: CoAsS · molar mass: 165.92 g/mol
| As | 45.16% | |
| Co | 35.52% | |
| S | 19.32% |
Computed from atomic weights (IUPAC 2021). Site-occupancy groups (Fe,Mn) split equally.
Mohs Hardness
5.5
Cobaltite sits at 5.5 on the Mohs scale — just hard enough to scratch glass.
Colors:
Streak
Gray-black
Gray-black
Crystal system
Orthorhombic (pseudo-cubic)
Orthorhombic (pseudo-cubic)
Sulfides & SulfosaltsSulfides
TL;DR · 1 min read
Cobaltite (CoAsS) is the cobalt arsenide-sulfide — pyrite-group structurally and visually similar to pyrite but with diagnostic cobalt content. It forms in high-temperature hydrothermal Co-Ni-Ag-As-Bi "five-element" vein assemblages.
Cobaltite (CoAsS) is the cobalt arsenide-sulfide — pyrite-group structurally and visually similar to pyrite but with diagnostic cobalt content. It forms in high-temperature hydrothermal Co-Ni-Ag-As-Bi “five-element” vein assemblages. Tunaberg (Sweden) and Cobalt (Ontario, Canada) supplied historic collector specimens; Bou Azzer (Morocco) is the modern source.