Formula: Ca19(Al,Fe)10(Mg,Fe)3(Si2O7)(SiO4)10(O,OH,F)10
Reflected/transmitted colour: colourless to pale yellow, green, brown or pinkish brown
Pleochroism: coloured varieties may show weak pleochroism, e.g. brownish yellow to yellowish brown
Optical isotropy/anisotropy: uniaxial
Optical sign: -
Refractive indices: ε = 1.700-1.746, w = 1.703-1.752
Birefringence δ: 0.001-0.009
2V angle:
Dispersion: strong
Optical orientation:
Optical axial plane:
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