Formula: Ba4(Fe,Ti,Fe,Mg)4(B2Si8O27)O2Clx
Reflected/transmitted colour:
Pleochroism: Strong, pale pinkish to flesh red (X=Y), dark brown to nearly black (Z)
Optical isotropy/anisotropy: Biaxial
Optical sign: +
Refractive indices: α = 1.770, β = 1.774, γ = 1.830
Bireflectance/Birefringence δ: 0.060
2V angle: 32° (calculated), 40° (measured)
Dispersion: Distinct, r > v
Optical orientation:
Optical axial plane:
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