Formula: Na2NaMn2Mg2(Al,Fe)2(PO4)6
Reflected/transmitted colour:
Pleochroism: Strong, light yellowish green (x), jade green (y), dark bluish green (z)
Optical isotropy/anisotropy: Biaxial
Optical sign: +
Refractive indices: α = 1.678, β = 1.684, γ = 1.691-1.91
Bireflectance/Birefringence δ: 0.013-0.232
2V angle: 22-86° (calculated), 79-80° (measured),
Dispersion: Strong, r >> v
Optical orientation:
Optical axial plane:
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