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| Formula | Na2Ca(Mg,Fe2+,Mn,Fe3+)5Si8O22(OH,F)2 - Na2Ca(Fe2+,Mg,Mn,Fe3+)5Si8O22(OH,F)2 |
| | Optic class & sign | Biaxial negative |
| | Optical orientation | |
| | Optical plane | |
| | Relief | |
| | Refractive indices | nx = 1.612 -1.646
|
|
ny = 1.623 -1.653
|
|
nz = 1.627 -1.660
|
|
| |
| | Birefringence (max.) | 0.014 - 0.025 |
| | | |
| | Optic Angle
| 2Vx
= 55 - 76° |
| | 2Vz
|
| | Sign of elongation | |
| | Interference figure | |
| | Colour / pleochroism | |
| | Zoning | |
|
|
| Form | Habit | |
| | | Surface | |
| | Cleavage | |
| | Twinning | |
| | Extinction | |
|
|
| Reaction textures | |
| | Alteration / decomposition | |
|
|
| Occurence | Ign | |
| | | Met | |
| | | Sed | |
| | | Hyd | |
| | | Other | |
|
|
| Distinctive properties | |
| | Additional comments | Few optical data available on natural specimens. n-Δn diagram: plotted data are from Deer at al., Vol. 2B (1997). Data for synthetic richterites: F-free richterite (Rct) and ferro-richterite (Frct) from Charles (1974), Am. Mineralogist 59, 518-528; Fluor-richterite (Flrct) from Gibbs et al. (1962), Am. Mineralogist 47, 75-82. |
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