|
| Formula | SrSO4 |
| | Optic class & sign | Biaxial positive |
| | Optical orientation | X = c, Y = b, Z = a |
| | Optical plane | (010) |
| | Relief | Moderate-positive |
| | Refractive indices | nx = 1.619 -1.622
|
|
ny = 1.622 -1.624
|
|
nz = 1.630 -1.632
|
|
| n increases with increasing Ba |
| | Birefringence (max.) | 0.009 - 0.010 |
| | | - |
| | Optic Angle
| 2Vx
|
| | 2Vz
= 51° - |
| | Sign of elongation | Not diagnostic as crystals may be elongate ∥ a, b, or c |
| | Interference figure | Sections ∥ (100) yield centred acute bisectrix figures on a first-order white background |
| | Colour / pleochroism | Colourless; may be faintly tinted |
| | Zoning | |
|
|
| Form | Habit | Tabular, lath-like, granular, fibrous aggregates |
| | | Surface | Euhedral to subhedral |
| | Cleavage | {001} perfect, 2 sets of {210} distinct |
| | Twinning | Rare |
| | Extinction | Straight or symmetrical to various morphological elements (traces of cleavages and faces), depending on section orientation |
|
|
| Reaction textures | |
| | Alteration / decomposition | Strontianite |
|
|
| Occurence | Ign | |
| | | Met | |
| | | Sed | Evaporitic sediments associated with anhydrite or gypsum deposits; disseminated in limestone and dolomite; precipitates in fissures and cavities |
| | | Hyd | Hydrothermal veins |
| | | Other | |
|
|
| Distinctive properties | Low birefringence, relief, high symmetry |
| | Additional comments | |
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