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| Formula | (Na2,Ca,K2)Al2Si10O24 ∙ 7H2O
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| | Optic class & sign | Biaxial positive or negative |
| | Optical orientation | X = c, Y = a, Z = b |
| | Optical plane | (100) |
| | Relief | Moderate-negative |
| | Refractive indices | nx = 1.472 -1.483
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ny = 1.475 -1.485
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nz = 1.477 -1.487
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| | Birefringence (max.) | 0.004 - 0.005 |
| | | |
| | Optic Angle
| 2Vx
= 76 - 90° |
| | 2Vz
= 90 - 76° |
| | Sign of elongation | Length-fast, l (-) |
| | Interference figure | Indistinct due to very low birefringence |
| | Colour / pleochroism | Colourless |
| | Zoning | |
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| Form | Habit | Fibrous to acicular; radiating or felty aggregates |
| | | Surface | |
| | Cleavage | {100}, {010} |
| | Twinning | None |
| | Extinction | Straight to traces of prism faces and cleavage in prismatic sections; straight to cleavage sets in sections ⊥c |
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| Reaction textures | |
| | Alteration / decomposition | Relatively stable under surface conditions |
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| Occurence | Ign | |
| | | Met | |
| | | Sed | Authigenic in detrital marine sediments |
| | | Hyd | Cavities (vesicles, amygdales, fractures) in mafic volcanic rocks; alteration product of volcanic glass |
| | | 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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