|
| Formula | SrCO3 |
| | Optic class & sign | Biaxial negative |
| | Optical orientation | X = c, Y = b, Z = a |
| | Optical plane | (010) |
| | Relief | Low-negative to moderate-positive |
| | Refractive indices | nx = 1.517 -1.520
|
|
ny = 1.663 -1.667
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|
nz = 1.667 -1.669
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|
| n increases with increasing Ca content (solubility towards aragonite) |
| | Birefringence (max.) | 0.149 - 0.150 |
| | | Increasing Ca does not affect Δn notably |
| | Optic Angle
| 2Vx
= 7 - 10° |
| | 2Vz
|
| | Sign of elongation | Length-fast, l (-) |
| | Interference figure | Sections ⊥ c show acute bisectrix figures with very low 2V and numerous isochromes |
| | Colour / pleochroism | Colourless |
| | Zoning | - |
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|
| Form | Habit | Granular, columnar, acicular, fibrous |
| | | Surface | Euhedral to subhedral |
| | Cleavage | {110}, two sets, intersecting at 64° |
| | Twinning | {110} simple, lamellar, or cyclic as sixlings |
| | Extinction | Straight to traces of prism faces and cleavage in sections ∥ c; symmetrical to cleavage in sections ⊥ c |
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|
| Reaction textures | |
| | Alteration / decomposition | Celestine; strontianite can be itself an alteration product of celestine |
|
|
| Occurence | Ign | Carbonatites |
| | | Met | Metamorphic Mn deposits |
| | | Sed | Concretions in limestone and calcareous clays |
| | | Hyd | Low-temperature veins and cavities in limestone and calcareous clays; gangue mineral in hydrothermal sulfide deposits |
| | | Other | |
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|
| Distinctive properties | Extreme birefringence with high-order white interference colours and marked change of relief with rotation in sections at a low angle to c; characteristic cleavage, extinction behaviour; biaxial character, twinning. |
| | Additional comments | n-Δn chart: Arg - aragonite, Cer - cerussite, Str - strontianite, Wth - witherite |
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