Formula: NaCa2(Fe,Mn)4MgFe(PO4)6.2H2O
Reflected/transmitted colour:
Pleochroism: Strong, blue (x), greenish blue (y), pale yellowish brown (z)
Optical isotropy/anisotropy: Biaxial
Optical sign: +
Refractive indices: α = 1.713, β = 1.718, γ = 1.728
Bireflectance/Birefringence δ: 0.015
2V angle: 72° (calculated), 66° (measured)
Dispersion: Strong, r < v
Optical orientation: α = a, β = b, γ = c
Optical axial plane:
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