Formula: (K,Na,NH4)3(AlFe3+)5(PO4)2(PO3OH)6.18H2O
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: Uniaxial
Optical sign: -
Refractive indices: ε = 1.500-1.503, ω = 1.506-1.510
Bireflectance/Birefringence δ: 0.060-0.070
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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