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: Cr1, Na1.00Na1.97Mg.03Mg4.03Cr.97Si8O22F2
_database_code_amcsd 0002059
9.722 17.813 5.282 90 103.69 90 C2/m
atom       x     y     z occ Biso
Si(1)  .2834 .0859 .2939      .43
Si(2)  .2898 .1719 .8018      .46
Mg(1)      0 .0895    .5      .53
Cr(2)      0 .1782     0 .49  .45
Mg(2)      0 .1782     0 .51  .45
Mg(3)      0     0     0      .55
Mg(4)      0 .2743    .5 .05 1.23
Na(4)      0 .2743    .5 .95 1.23
NaA        0    .5     0 .27 1.91
NaA(m) .0442    .5 .0930 .27 2.13
NaA(2)     0 .4725     0 .10 2.74
O1     .1130 .0870 .2134      .62
O2     .1188 .1678 .7335      .58
F3     .1041     0 .7068      .80
O4     .3620 .2512 .7977      .82
O5     .3527 .1291 .0838      .74
O6     .3445 .1191 .5844      .73
O7     .3421     0 .2935      .78