Formula: (Ce,La)2Al(SiO4)2(OH)
Reflected/transmitted colour:
Pleochroism: Ce: Very strong, light rose to greenish yellow (X), bluish green (Y), light rose (Z)
La: Extreme, strong bluish green (X), yellow-green (Y), pinkish (Z)
Optical isotropy/anisotropy: Biaxial
Optical sign: +
Refractive indices: Ce: α = 1.845, β = 1.852, γ = 1.878
La: α = 1.808, β = 1.812, γ = 1.838
Bireflectance/Birefringence δ: Ce: 0.033, La: 0.030
2V angle: 56° (calculated), 20-40° (measured)
Dispersion: Very strong, r < v (Ce), r > v (La)
Optical orientation:
Optical axial plane:
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