Formula: (Na,Ca)Mn(Mn,Fe,Fe)2(PO4)3
Reflected/transmitted colour:
Pleochroism: Yellow green (x) grass green (z)
Optical isotropy/anisotropy: Biaxial
Optical sign: +
Refractive indices: α = 1.708, γ = 1.722
Bireflectance/Birefringence δ: 0.014
2V angle: 70° (measured)
Dispersion: r > v
Optical orientation:
Optical axial plane:
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