Formula: Be3SiO4(OH)2 . H2O
Reflected/transmitted colour:
Pleochroism:
Optical isotropy/anisotropy: biaxial
Optical sign: -
Refractive indices: a = 1.50-1.544, b = 1.553, g = 1.52-1.562
Birefringence δ: 0.02
2V angle: < 45°
Dispersion:
Optical orientation:
Optical axial plane:
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