Formula: Na4Mn4Si8(O,OH)24.9H2O
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: Biaxial
Optical sign: -
Refractive indices: α = 1.54, β = 1.542, γ = 1.55
Bireflectance/Birefringence δ: 0.01
2V angle: 54° (calculated), 53° (measured)
Dispersion:
Optical orientation:
Optical axial plane:
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