Formula: (K,Na)2(Fe,Mg)5Si12O30
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: Uniaxial
Optical sign: -
Refractive indices: ε = 1.559-1.592, ω = 1.570
Bireflectance/Birefringence δ: 0.011-0.022
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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