Formula: NaNa2(Mn2Mn3)Si8O22O2
Reflected/transmitted colour:
Pleochroism: Orange red (x), very dark red (y), very dark red (z)
Optical isotropy/anisotropy: Biaxial
Optical sign: -
Refractive indices: α = 1.717, β = 1.78, γ = 1.80
Bireflectance/Birefringence δ: 0.083
2V angle: 56° (calculated), 57° (measured)
Dispersion: r < v
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 |