Formula: S
Reflected/transmitted colour: yellowish to colourless, polished section grayish
Pleochroism: distinct
Optical isotropy/anisotropy: biaxial, polished section distinct anisotropy, only observable in air, in oil masked by internal reflections
Optical sign: +
Refractive indices: α = 1.958, β = 2.038, γ = 2.245
Birefringence δ/bireflectance: ~ 0.287, polished section distinct, only observable in air, with nicols not completely crossed, in oil masked by internal reflections
2V angle: 68-69°
Dispersion: r < v
Optical orientation: α = x, β = y, γ = z
Optical axial plane:
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