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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
|
|
ny = 1.592 -1.624
|
|
nz = 1.596 -1.645
|
|
| 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 | |
|
|
| Form | Habit | Equant, short- to long-prismatic |
| | | Surface | |
| | Cleavage | {100}, {110} |
| | Twinning | Multiple twins on {111} common |
| | Extinction | Inclined |
|
|
| Reaction textures | |
| | Alteration / decomposition | |
|
|
| Occurence | Ign | Granite pegmatite |
| | | Met | |
| | | Sed | |
| | | Hyd | Veins, greisen |
| | | Other | |
|
|
| Distinctive properties | Relief, Δn, twinning, low symmetry, restricted occurrence |
| | Additional comments | |
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