Stillwellite-(Ce)
| Stillwellite-(Ce) | |
|---|---|
1.3 cm stillwellite-(Ce) crystal in matrix | |
| General | |
| Category | Silicate mineral |
| Formula | (Ce,La,Ca)BSiO5 |
| IMA symbol | Swl |
| Strunz classification | 9.AJ.25 |
| Dana classification | 54.02.03.02 |
| Crystal system | Trigonal |
| Crystal class | Pyramidal (3) H-M symbol: (3) |
| Space group | P31 |
| Identification | |
| Color | Red-brown to pale pink |
| Crystal habit | Flat rhombohedral crystals, massive |
| Twinning | Observed on {100} |
| Cleavage | Imperfect |
| Fracture | Conchoidal |
| Mohs scale hardness | 6.5 |
| Luster | Resinous |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 4.57–4.6 |
| Optical properties | Uniaxial (+) |
| Refractive index | nω = 1.765, nε = 1.780 |
| Birefringence | δ = 0.015 |
| Other characteristics | Radioactive |
| References | |
Stillwellite-(Ce) is a rare-earth boro-silicate mineral with chemical formula (Ce,La,Ca)BSiO5.