Formula: Ca19(Al,Mg)13(B,Al)5Si18O68(O,OH,F)10
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: Uniaxial
Optical sign: +
Refractive indices: ω = 1.721, ε = 1.725
Bireflectance/Birefringence δ: 0.004
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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