Formula: MnVAlSi2O6(OH)4
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: Biaxial
Optical sign: +
Refractive indices: α = 1.684, β = 1.691 (calc.), γ = 1.700
Bireflectance/Birefringence δ: 0.016
2V angle: 85° (measured)
Dispersion:
Optical orientation:
Optical axial plane:
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