Formula: Mg(OH,F)2.3Mg2(SiO4)
Reflected/transmitted colour: colourless to yellow-brown
Pleochroism: α very pale to dark yellow, β colourless, pale yellow, γ colourless, pale yellow
Optical isotropy/anisotropy: biaxial
Optical sign: +
Refractive indices: α = 1.607-1.643, β = 1.619-1.655, λ = 1.639-1.675
Birefringence δ: 0.029-0.031
2Vγ angle: 65-84°
Dispersion: r > v
Optical orientation: α = a, β = z, γ = y
Optical axial plane: (001)
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