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| Formula | Ca2NaAl5Si5O20 ∙ 6H2O
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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 = 1.497 -1.530
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ny = 1.513 -1.533
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nz = 1.518 -1.545
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| n increases with substitution of CaAl for NaSi |
| | Birefringence (max.) | 0.015 - 0.021 |
| | | Δn increases with substitution of CaAl for NaSi |
| | Optic Angle
| 2Vx
|
| | 2Vz
= 42 - 75° |
| | Sign of elongation | Length-slow, l (+) and length-fast l (-) as c = Y |
| | Interference figure | In sections ∥c melatopes are aligned orthogonal to c |
| | Colour / pleochroism | Colourless |
| | Zoning | |
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| Form | Habit | Fibrous to columnar, radiating or parallel-grown aggregates |
| | | Surface | |
| | Cleavage | {010}, {100} |
| | Twinning | Rare |
| | Extinction | Straight to traces of prism faces and cleavage in prismatic sections; straight to traces of [100} and {010} faces and cleavage sets in sections ⊥c |
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| Reaction textures | Replaces nepheline and Ca-rich plagioclase |
| | Alteration / decomposition | Montmorillonite clays; relatively stable under surface conditions |
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| Occurence | Ign | |
| | | Met | Contact-metamorphic limestone |
| | | Sed | Lacustrine and marine sediments |
| | | Hyd | Cavities (vesicles, amygdales, fractures) in mafic volcanic rocks, hydrothermally altered 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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