Formula: Fe4(AsO4)3(SO4)(OH).15H2O
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: Biaxial
Optical sign: -
Refractive indices: α = 1.632, β = 1.635-1.636, γ = 1.646
Bireflectance/Birefringence δ: 0.014
2V angle: 56-66° (calculated), 60° (measured)
Dispersion:
Optical orientation:
Optical axial plane:
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