Formula: (Mg,Fe,Ca)(Mg,Fe)(Si2O6)
Reflected/transmitted colour: pale yellow green
Pleochroism: often absent, but may be weak to moderate, α colourless, pale green, yellowish green or smoky brown, β pale brown, pale brownish green, brownish pink or smoky brown, γ colourless, pale green or pale yellow
Optical isotropy/anisotropy: biaxial
Optical sign: +
Refractive indices: α = 1.682-1.732, β = 1.684-1.732, γ = 1.705-1.757
Birefringence δ: 0.023-0.029
2Vγ angle: 0-30°
Dispersion: r < v or r > v, moderate
Optical orientation: α = y, γ Λ z = 37-44° (more rarely β = y)
Optical axial plane: ┴ (010) [when β = y (010)]
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