Formula: (Fe,Mg)2(Mg,Fe)3Si12O30
Reflected/transmitted colour:
Pleochroism: Strong, deep blue (O), yellowish green (E)
Optical isotropy/anisotropy: Uniaxial
Optical sign: -
Refractive indices: ω = 1.589, ε = 1.586
Bireflectance/Birefringence δ: 0.003
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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