AM_Fluoro-eckermannite_4 Formula: Si8 Mg4.12 Cr.98 Na2.91 O22 F2 Name: Fluoro-eckermannite Unit cell: 9.722 17.813 5.282 90.0 103.69 90.0 , V=888.74 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: Cr1, Na1.00Na1.97Mg.03Mg4.03Cr.97Si8O22F2