Formula: Mn2SiO4
Reflected/transmitted colour: Pale brown, may be colourless
Pleochroism: None or weak, brownish red (X), reddish (Y), greenish blue (Z)
Optical isotropy/anisotropy: Biaxial
Optical sign: +
Refractive indices: α = 1.770-1.788, β = 1.807-1.810, γ = 1.817-1.825
Bireflectance/Birefringence δ: 0.037-0.055
2V angle: 78° (calculated), 60-70° (measured)
Dispersion: r > v
Optical orientation: X = b, Y = c, Z = a
Optical axial plane:
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