Formula: Mg5(BO3)O(OH)5.2H2O
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: Biaxial
Optical sign: -
Refractive indices: α = 1.585, β = 1.603, γ = 1.604
Bireflectance/Birefringence δ: 0.019
2V angle: 26° (calculated), 33° (measured)
Dispersion: Strong, r < v
Optical orientation: Z Ù c = 5°
Optical axial plane:
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