Fluoro-eckermannite Oberti R, Hawthorne F C, Camara F, Raudsepp M American Mineralogist 84 (1999) 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 _database_code_amcsd 0002060 9.728 17.825 5.278 90 103.66 90 C2/m atom x y z occ Biso Si(1) .2835 .0857 .2924 .37 Si(2) .2897 .1718 .7999 .37 Mg(1) 0 .0898 .5 .51 Cr(2) 0 .1785 0 .38 .34 Mg(2) 0 .1785 0 .62 .34 Mg(3) 0 0 0 .38 Mg(4) 0 .2740 .5 .05 1.35 Na(4) 0 .2740 .5 .95 1.35 NaA 0 .5 0 .27 1.99 NaA(m) .0402 .5 .0946 .09 2.38 NaA(2) 0 .4743 0 .08 2.22 Mg(4') 0 .2441 .5 .04 .41 O1 .1128 .0859 .2136 .52 O2 .1189 .1678 .7316 .50 F3 .1029 0 .7091 .62 O4 .3618 .2510 .7947 .85 O5 .3522 .1294 .0828 .69 O6 .3445 .1188 .5826 .75 O7 .3430 0 .2909 .71