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Formula | LiAl(PO)4(F,OH) |
| Optic class & sign | Biaxial positive or negative |
| Optical orientation | X near b, Y near a, Z near c |
| Optical plane | Approx parallel to b |
| Relief | Moderate- positive |
| Refractive indices | nx = 1.577 -1.615
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ny = 1.592 -1.624
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nz = 1.596 -1.645
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n increases with replacement of F by OH |
| Birefringence (max.) | 0.019 - 0.031 |
| | Δ:n increases with replacement of F by OH |
| Optic Angle
| 2Vx
= 66 - 90° |
| 2Vz
= 90 - 40° |
| Sign of elongation | Length-slow, l (+) |
| Interference figure | |
| Colour / pleochroism | Colourless |
| Zoning | |
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Form | Habit | Equant, short- to long-prismatic |
| | Surface | |
| Cleavage | {100}, {110} |
| Twinning | Multiple twins on {111} common |
| Extinction | Inclined |
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Reaction textures | |
| Alteration / decomposition | |
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Occurence | Ign | Granite pegmatite |
| | Met | |
| | Sed | |
| | Hyd | Veins, greisen |
| | Other | |
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Distinctive properties | Relief, Δn, twinning, low symmetry, restricted occurrence |
| Additional comments | |
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