Formula: MgFe2(PO4)2(OH)2.8 H2O
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: Biaxial
Optical sign: -
Refractive indices: α = 1.584, β = 1.637, γ = 1.67
Bireflectance/Birefringence δ: 0.086
2V angle: 74° (calculated), 50° (measured)
Dispersion: Strong, r > v
Optical orientation: Y Ù c =26°, X and Y nearly in {010}
Optical axial plane:
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