Formula: Ca7Mg(SiO4)4
Reflected/transmitted colour: colourless to very pale violet
Pleochroism: weak, in thick sections a = pale violet, b = g = colourless to pale green
Optical isotropy/anisotropy: biaxial
Optical sign: +
Refractive indices: a = 1.712-1.725, b = 1.716-1.728, g = 1.725-1.740
Birefringence δ: 0.013-0.028
2V angle: 10-34°
Dispersion:
Optical orientation: a = b, b = a, g = c
Optical axial plane:
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