Enargite
Enargite is a copper arsenic sulfosalt mineral with formula Cu3AsS4. It takes its name from the Greek word enarge, "distinct". Enargite is a steel gray, blackish gray, to violet black mineral with metallic luster. It forms slender orthorhombic prisms as well as massive aggregates. It has a hardness of 3 and a specific gravity of 4.45.
| Enargite | |
|---|---|
| General | |
| Category | Sulfosalt mineral |
| Formula (repeating unit) | Cu3AsS4 |
| IMA symbol | Eng |
| Strunz classification | 2.KA.05 |
| Crystal system | Orthorhombic |
| Crystal class | Pyramidal (mm2) H-M symbol: (mm2) |
| Space group | Pmn21 |
| Unit cell | a = 7.407(1), b = 6.436(1) c = 6.154(1) [Å]; Z = 2 |
| Identification | |
| Color | Grayish black to iron black; gray to pale pink-brown, deep red internal reflections in polished section |
| Crystal habit | Tabular to prismatic crystals, striated parallel to {001}; massive |
| Twinning | Twin plane {320} common, rarely as interpenetrating pseudohexagonal trillings |
| Cleavage | Perfect on {110}, distinct {100} and {010} |
| Fracture | Uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 3 |
| Luster | Metallic to dull |
| Streak | Black |
| Diaphaneity | Opaque |
| Specific gravity | 4.4 to 4.5 |
| References | |
Enargite is dimorph of the tetragonal luzonite.
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