Formula: NaCa2Al5Si5O20.6H2O
Reflected/transmitted colour: Colourless
Pleochroism:
Optical isotropy/anisotropy: Biaxial
Optical sign: +
Refractive indices: α = 1.511-1.53, β = 1.513-1.532, γ = 1.516-1.545
Bireflectance/Birefringence δ: 0.005-0.015
2V angle: 44-80° (calculated), 44-75° (measured)
Dispersion: Strong, r > v
Optical orientation: X = a, Y = c, Z = b
Optical axial plane:
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