Formula: (Na,Ca,K)4Ti4(Si,Al)8O26.(H2O,Na)
Reflected/transmitted colour:
Pleochroism: Colourless (x), brownish (y), brownish (z)
Optical isotropy/anisotropy: Biaxial
Optical sign: -
Refractive indices: α = 1.691-1.745, β = 1.769-1.773, γ = 1.773-1.818
Bireflectance/Birefringence δ: 0.073-0.082
2V angle: 24-80° (calculated), 41-82° (measured)
Dispersion:
Optical orientation:
Optical axial plane:
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