Celestine (mineral)
(Redirected from Celestite)
| Celestine | |
|---|---|
 Clear grey-blue celestine crystals | |
| General | |
| Category | Sulfate minerals |
| Formula | SrSO4 sometimes contains minor calcium and/or barium |
| IMA symbol | Clt[1] |
| Strunz classification | 7.AD.35 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pnma |
| Unit cell | a = 8.359 Å, b = 5.352 Å, c = 6.866 Å; Z = 4 |
| Identification | |
| Color | White, pink, pale green, pale brown, black, pale blue, reddish, greyish; colourless or lightly tinted in transmitted light |
| Crystal habit | Tabular to pyramidal crystals, also fibrous, lamellar, earthy, massive granular |
| Cleavage | Perfect on {001}, good on {210}, poor on {010} |
| Fracture | Uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 3.0–3.5 |
| Luster | Vitreous, pearly on cleavages |
| Streak | white |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.95–3.97 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.619–1.622 nβ = 1.622–1.624 nγ = 1.630–1.632 |
| Birefringence | δ = 0.011 |
| Pleochroism | Weak |
| 2V angle | Measured: 50°–51° |
| Dispersion | Moderate r < v |
| Ultraviolet fluorescence | yellow, white blue (both short and long UV) |
| References | [2][3][4][5] |