Formula: (Mn,Ca,Fe)SiO3
Reflected/transmitted colour: colourless to faint pink
Pleochroism: weak, in thick sections α yellowish red, β pinkish red, γ pale yellowish red
Optical isotropy/anisotropy: biaxial
Optical sign: +
Refractive indices: α = 1.711-1.734, β = 1.716-1.739, γ = 1.724-1.748
Birefringence δ: 0.011-0.017
2Vγ angle: 63-87°
Dispersion: r < v
Optical orientation: α Λ x = ~5°, β Λ y = ~20°, γ Λ z = ~ 25°
Optical axial plane:
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