AM_Fluoro-eckermannite_5
Formula: Si8 Mg4.42 Cr.76 Na2.51 O22 F2
Name: Fluoro-eckermannite
Unit cell: 9.728 17.825 5.278 90.0 103.66 90.0 , V=889.33
Space group: C12/M1 (12)

Oberti R , Hawthorne F C , Camara F , Raudsepp M , American Mineralogist , 84 (1999) p.102-111, Unusual M3+ cations in synthetic amphiboles with nominal fluoro-eckermannite, composition: Deviations from stoichiometry and structural effects of the, cummingtonite component, Sample: Cr2, Na1.00Na1.75Mg.25Mg4.25Cr.75Si8O22F2