|
| Formula | (Ce,La,Th)PO4 |
| | Optic class & sign | Biaxial positive |
| | Optical orientation | X = b, Y near a, Z near c |
| | Optical plane | (010) |
| | Relief | High |
| | Refractive indices | nx = 1.772 -1.800
|
|
ny = 1.778 -1.801
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|
nz = 1.823 -1.860
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|
| n increases with Th content |
| | Birefringence (max.) | 0.045 - 0.075 |
| | | - |
| | Optic Angle
| 2Vx
|
| | 2Vz
= 6 - 26° |
| | Sign of elongation | Length-fast, l (-) for crystals elongate in b |
| | Interference figure | Sections ⊥ c show acute bisectrix figure with small 2V and numerous isochromes |
| | Colour / pleochroism | Colourless to pale yellow or yellow-brown; weak pleochroism |
| | Zoning | |
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| Form | Habit | Granular-blocky, thick-tabular, may be elongate parallel to b |
| | | Surface | Euhedral, subhedral |
| | Cleavage | {100} |
| | Twinning | Simple on {100} |
| | Extinction | Inclined to cleavage; small extinction angle c∧Z = 2-7° |
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| Reaction textures | |
| | Alteration / decomposition | Relatively stable in surface environments |
|
|
| Occurence | Ign | Felsic plutonic rocks |
| | | Met | Schists, gneisses, granulites, marble |
| | | Sed | Detrital in clastic sediments; heavy mineral fraction of sands |
| | | Hyd | Veins |
| | | Other | |
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|
| Distinctive properties | High n, high Δn |
| | Additional comments | Commonly present in accessory amounts only |
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Images 
