Formula: Na8Mn2Si10O25(OH,Cl)2.12H2O
Reflected/transmitted colour: Yellow
Pleochroism: Pale yellow (x,y), yellowish green (z)
Optical isotropy/anisotropy: Biaxial
Optical sign: +
Refractive indices: α = 1.532, β = 1.540, γ = 1.550
Bireflectance/Birefringence δ: 0.018
2V angle: 86° (calculated), 89° (measured)
Dispersion: Weak, r < v
Optical orientation:
Optical axial plane:
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