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| Formula | Na2Ca2Al6Si9O30 ∙ 8H2O
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| | Optic class & sign | Biaxial positive |
| | Optical orientation | X = a, Y = c, Z = b |
| | Optical plane | (001) |
| | Relief | Low-negative |
| | Refractive indices | nx = 1.504 -1.508
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ny = 1.504 -1.508
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nz = 1.505 -1.509
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| - |
| | Birefringence (max.) | <0.001 |
| | | - |
| | Optic Angle
| 2Vx
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| | 2Vz
= 80° - |
| | Sign of elongation | Length-slow, l (+), and length-fast, l (-) |
| | Interference figure | Near-impossible to obtain due to crystal habit and extremely low birefringence |
| | Colour / pleochroism | Colourless |
| | Zoning | |
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| Form | Habit | Fibrous, acicular |
| | | Surface | Euhedral to subhedral |
| | Cleavage | 2 sets {130} |
| | Twinning | (100) and (010), generally present |
| | Extinction | Straight to traces of prism faces and {110} cleavage in prismatic sections; symmetrical to traces of {110} 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 | |
| | | Sed | |
| | | Hyd | Cavities (vesicles, amygdales, fractures) in mafic volcanic rocks |
| | | Other | |
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| Distinctive properties | |
| | 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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