|
| Formula | Ca5(SiO4)2CO3 |
| | Optic class & sign | Biaxial negative |
| | Optical orientation | X = b, Y∧a = 33°, Z near c |
| | Optical plane | Orthogonal to (010) |
| | Relief | Moderate-positive (to high) |
| | Refractive indices | nx = 1.637-1.641
|
|
ny = 1.672 -1.676
|
|
nz = 1.676 -1.681
|
|
|
| | Birefringence (max.) | 0.039 - 0.040 |
| | | |
| | Optic Angle
| 2Vx
= 38 - 41° |
| | 2Vz
|
| | Sign of elongation | Length-slow, l (+) |
| | Interference figure | |
| | Colour / pleochroism | Colourless |
| | Zoning | - |
|
|
| Form | Habit | Granular, columnar |
| | | Surface | |
| | Cleavage | {001} |
| | Twinning | Lamellar on {001} and {101}; also simple, at 57-58° |
| | Extinction | |
|
|
| Reaction textures | |
| | Alteration / decomposition | |
|
|
| Occurence | Ign | |
| | | Met | Siliceous calcareous rocks in high-temperature contact-metamorphic zones |
| | | Sed | |
| | | Hyd | |
| | | Other | |
|
|
| Distinctive properties | High Δn, negative optic sign, low 2V; restricted occurrence in high-T contact zones |
| | Additional comments | There is very little information in the literature on natural crystal habits of spurrite. Hence, the crystal diagrams are purely schematic. |
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