Formula: (Ce,Y,Ca)5(SiO4,PO4)3(OH,F)
Reflected/transmitted colour: colourless to brownish (-Ce), yellowish brown (-Y)
Pleochroism: may be w = brown, e = colourless (-Ce)
Optical isotropy/anisotropy: uniaxial
Optical sign: - (-Ce) or + (-Y)
Refractive indices: n = 1.77-1.81 (-Ce), w = 1.728, e = 1.730-1.72 (-Y)
Birefringence δ: very low
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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