Formula: Ca2(Mg,Mn)2B4O7(OH)6
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: Biaxial
Optical sign: -
Refractive indices: α = 1.619, β = 1.627, γ = 1.629
Bireflectance/Birefringence δ: 0.010
2V angle: 52° (calculated), 48° (measured)
Dispersion:
Optical orientation:
Optical axial plane:
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