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| Formula | CaF2 |
| | Optic class & sign | Isotropic |
| | Relief | Moderate, negative |
| | Refractive Index | 1.433 -1.435
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| Substitution of REE (mainly Y) for Ca increases n (highest reported value 1.47) |
| | Birefringence | Zero; may show weak anomalous birefringence |
| | Colour | Colourless, pale green, pale to deep violet-blue or purple; colour zoning is common in coloured crystals |
| | Zoning | |
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| Form | Habit | Equant (cubes, octahedra, dodecahedra), also columnar to fibrous in banded zones or spheroidal aggregates |
| | | Surface | Euhedral to anhedral |
| | Cleavage | {111} perfect (4 sets) |
| | Twinning | {111} common, penetration twins or spinel-type contact twins; can only be recognised in thin section from characteristic crystal outlines (or colour zoning patterns) |
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| Reaction textures | |
| | Alteration / decomposition | Soluble; pseudomorphs after fluorite are common |
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| Occurence | Ign | Greisenized granite, pegmatites, carbonatites |
| | | Met | Not common |
| | | Sed | Detrital in sands, authigenic in evaporites |
| | | Hyd | Veins and cavities in granitic to alkaline igneous rocks (and their wall rocks), carbonatites and sedimentary carbonate rocks; hydrothermal replacement deposits, hot spring deposits; rarely as cement in clastic sedimentary rocks |
| | | Other | |
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| Distinctive properties | Moderate-negative relief, isotropic, characteristic cleavage, colour if present |
| | Additional comments | |
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