Formula: Be4Si2O7(OH)2
Reflected/transmitted colour: colourless
Pleochroism:
Optical isotropy/anisotropy: biaxial
Optical sign: -
Refractive indices: a = 1.583-1.591, b = 1.598-1.605, g = 1.608-1.614
Birefringence δ: 0.017-0.04
2V angle: ~ 75°
Dispersion: r < v, weak
Optical orientation: a = a, b = b
Optical axial plane:
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