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| Formula | CaAl2Si3O10 ∙ 3H2O
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| | Optic class & sign | Biaxial negative |
| | Optical orientation | X near c, Y near a, Z = b |
| | Optical plane | Orthogonal to (010) |
| | Relief | Low-negative |
| | Refractive indices | nx = 1.507 -1.513
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ny = 1.516 -1.520
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nz = 1.517 -1.521
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| - |
| | Birefringence (max.) | 0.008 - 0.010 |
| | | - |
| | Optic Angle
| 2Vx
= 36 - 56° |
| | 2Vz
|
| | Sign of elongation | Length-fast, l (-) |
| | Interference figure | Hard to obtain due to crystal habit and low birefringence |
| | Colour / pleochroism | Colourless |
| | Zoning | |
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| Form | Habit | Fibrous to acicular, radiating aggregates |
| | | Surface | Euhedral to subhedral |
| | Cleavage | 2 sets {110} |
| | Twinning | {100} multiple |
| | Extinction | Inclined, c ∧ x 18°; symmetrical to traces of {110} crystal faces and cleavage in sections ⊥c |
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| Reaction textures | |
| | Alteration / decomposition | Relatively stable under surface conditions |
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| Occurence | Ign | |
| | | Met | Zeolite-facies carbonate rocks |
| | | Sed | |
| | | Hyd | Cavities (vesicles, amygdales, fractures) in mafic volcanic rocks |
| | | Other | |
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| Distinctive properties | Inclined extinction, negative sign of elongation |
| | Additional comments | n-Δn chart: Edi – edingtonite, Gon – gonnardite, Lmt – laumontite, Mes – mesolite, Mor – mordenite, Ntr – natrolite, Sco – scolecite, Thm - thomsonite |
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