Kermesite
Kermesite or antimony oxysulfide is also known as red antimony or purpur blende (Sb2S2O) . The mineral's color ranges from cherry red to a dark red to a black. Kermesite is the result of partial oxidation between stibnite (Sb2S3) and other antimony oxides such as valentinite (Sb2O3) or stibiconite (Sb3O6(OH)). Under certain conditions with oxygenated fluids the transformation of all sulfur to oxygen would occur but kermesite occurs when that transformation is halted.
| Kermesite | |
|---|---|
| General | |
| Category | Oxysulfide |
| Formula (repeating unit) | (Sb2S2O) |
| IMA symbol | Kem |
| Strunz classification | 2.FD.05 |
| Dana classification | 02.13.01.01 |
| Crystal system | Triclinic |
| Crystal class | Pinacoidal (1) (same H-M symbol) |
| Space group | P1 |
| Identification | |
| Color | Red to cherry red, purple |
| Crystal habit | Acicular, fibrous, radial |
| Cleavage | Perfect {100}, parting on {010} |
| Fracture | Brittle |
| Tenacity | Sectile |
| Mohs scale hardness | 1–2 |
| Luster | Adamantine to semimetallic |
| Streak | Brownish red |
| Diaphaneity | Translucent, Opaque |
| Specific gravity | 4.5–4.8+ |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 2.720 nβ = 2.740 nγ = 2.740 |
| Pleochroism | None |
| References | |
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