Ullmannite
Ullmannite is a nickel antimony sulfide mineral with formula: NiSbS. Considerable substitution occurs with cobalt and iron in the nickel site along with bismuth and arsenic in the antimony site. A solid solution series exists with the high cobalt willyamite.
| Category: | Sulfide mineral |
| Chemical Formula: | NiSbS |
| Nickel Antimony Sulfide | |
| Molecular Weight: | 212.51 gm |
| Composition: | Nickel | 27.62 % | Ni | ||
| Antimony | 57.29 % | Sb | |||
| Sulfur | 15.09 % | S | |||
| 100.00 % |
| Crystallography: | Isometric – Tetartoidal |
| Crystal Habit: | As cubes and, less commonly, octahedra, pyritohedra, tetrahedra, to 3 cm. Cube faces striated by [110], twin boundaries of enantiomorphs. |
| Twinning: | Forms penetration twins about [110] with {001} the approximate composition plane; re-entrants develop on cube edges. |
| Cleavage: | Perfect on {001} |
| Fracture: | Irregular/Uneven |
| Tenacity: | Brittle |
| Moh’s Hardness: | 5.0 – 5.5; Vickers: VHN100=592-627 kg/mm2 |
| Density: | 6.65 – 6.85 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Steel-gray to silver-white; white in reflected light |
| Transparency: | Opaque |
| Luster: | Metallic |
| Refractive Index: | R: (400) 52.0, (420) 51.0, (440) 50.0, (460) 49.0, (480) 48.2, (500) 47.4, (520) 46.7, (540) 46.1, (560) 45.7, (580) 45.5, (600) 45.5, (620) 45.6, (640) 46.0, (660) 46.4, (680) 47.0, (700) 47.6 |
| Birefringence: | 0.000 (opaque) |
| Dispersion: | None |
| Pleochroism: | None |
| Anisotropism: | Individuals may be weakly anisotropic revealing a fine lamellar structure. |
