Formula: (K,Na)(AlSi3O8)
Reflected/transmitted colour: colourless
Pleochroism: -
Optical isotropy/anisotropy: biaxial
Optical sign: - (monoclinic), - or + triclinic
Refractive indices: α = 1.518-1.527, β = 1.522-1.532, γ = 1.522-1.534
Birefringence δ: 0.006-0.008
2Vα angle: 60° [OAP //(010)] - 50° [OAP ┴ (010)]
Dispersion: variable
Optical orientation: α Λ x = 5°, β = y, γ Λ z = ~ 20°
Optical axial plane: //(010) (2V 60°), ┴ (010) (2V 50°)
| 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 |