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| Formula | CaAl2Si6O16 ∙ 4H2O |
| | Optic class & sign | Biaxial negative |
| | Optical orientation | X near c, Y near a, Z = b |
| | Optical plane | Optic plane ⊥ (010) |
| | Relief | Moderate-negative |
| | Refractive indices | nx = 1.492 -1.496
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|
ny = 1.497 -1.500
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|
nz = 1.502 -1.504
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| |
| | Birefringence (max.) | 0.008 - 0.010 |
| | | |
| | Optic Angle
| 2Vx
= 48 - 89° |
| | 2Vz
|
| | Sign of elongation | Length-fast, l (-), in elongate sections at a high angle to (010) |
| | Interference figure | |
| | Colour / pleochroism | Colourless |
| | Zoning | - |
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|
| Form | Habit | Thin tabular, also in parallel-grown clusters |
| | | Surface | |
| | Cleavage | Commonly not seen in thin section |
| | Twinning | None |
| | Extinction | Straight to traces of {010} faces in sections ∥ b |
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| Reaction textures | |
| | Alteration / decomposition | |
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| Occurence | Ign | |
| | | Met | |
| | | Sed | |
| | | Hyd | Cavities and fractures in basalts and andesites affected by hydrothermal activity |
| | | Other | |
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| Distinctive properties | Rare zeolite; characteristic habit, very low n, lack of cleavage |
| | Additional comments | n-Δn charts A, B: Bre - brewsterite, Cpt - clinoptilolite, Epi - epistilbite, Hul - heulandite,
Lev - levyne, Stb - stilbite, Yug - yugawaralite |
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