Formula: NaMg3Al6B3Si6(O,OH)30(OH,F)
Reflected/transmitted colour: yellow to colourless
Pleochroism: variable in intensity, normally very strong, absorption always w > ε
Optical isotropy/anisotropy: uniaxial
Optical sign: -
Refractive indices: ε = 1.612-1.632, w = 1.634-1.661
Birefringence δ: 0.021-0.029
2V angle:
Dispersion: weak
Optical orientation:
Optical axial plane:
| Back to Alphabetical list | Colour photos | Physical, chemical and crystallographic description | SEM images | TEM images | vibrational spectra description | IR spectra | Raman spectra | N-IR spectra | F-IR spectra | IES spectra |