Formula: Ca(Mn,Fe)(Si2O6)
Reflected/transmitted colour: colourless
Pleochroism: more iron-rich members may show weak pleochroism in pale greens, greenish brown, bluish green and yellow-green
Optical isotropy/anisotropy: biaxial
Optical sign: +
Refractive indices: α = 1.699-1.710, β = 1.710-1.719, γ = 1.725-1.738
Birefringence δ: 0.022-0.029
2Vγ angle: 58-72°
Dispersion: r < v or r > v, weak
Optical orientation: β = y, γ Λ z = 46-55°
Optical axial plane: (010)
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