Formula: (Mn,Ca,Fe)SiO3
Reflected/transmitted colour: colourless to yellowish pink
Pleochroism: weak, in thick sections α orange, β rose
Optical isotropy/anisotropy: biaxial
Optical sign: -
Refractive indices: α = 1.640-1.695, β = 1.651-1.708, γ = 1.653-1.710
Birefringence δ: 0.013-0.017
2Vα angle: 34-60°
Dispersion: r < v, weak to strong
Optical orientation: α Λ x = ~15°, β Λ y = ~35°, γ Λ z = ~30-35° and α approximately ┴ (100) (based on old choice of unit cell)
Optical axial plane: approximately ┴ (100)
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