Formula: (Na,Ca,Mn)(Fe,Mn)(Fe,Fe,Mg)Al(PO4)3
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: Biaxial
Optical sign: +
Refractive indices: α = 1.688, β = 1.691, γ = 1.696
Bireflectance/Birefringence δ: 0.008
2V angle: 76° (calculated), 50° (measured)
Dispersion: Strong, r < v
Optical orientation:
Optical axial plane:
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