data_global
_chemical_name_mineral 'Fluoro-eckermannite'
loop_
_publ_author_name
'Oberti R'
'Hawthorne F C'
'Camara F'
'Raudsepp M'
_journal_name_full 'American Mineralogist'
_journal_volume 84 
_journal_year 1999
_journal_page_first 102
_journal_page_last 111
_publ_section_title
;
 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
_chemical_formula_sum 'Si8 Mg4.42 Cr.76 Na2.51 O22 F2'
_cell_length_a 9.728
_cell_length_b 17.825
_cell_length_c 5.278
_cell_angle_alpha 90
_cell_angle_beta 103.66
_cell_angle_gamma 90
_cell_volume 889.326
_exptl_crystal_density_diffrn      3.060
_symmetry_space_group_name_H-M 'C 1 2/m 1'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '1/2+x,1/2+y,z'
  'x,-y,z'
  '1/2+x,1/2-y,z'
  '-x,y,-z'
  '1/2-x,1/2+y,-z'
  '-x,-y,-z'
  '1/2-x,1/2-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
_atom_site_U_iso_or_equiv
Si(1)   0.28350   0.08570   0.29240   1.00000   0.00469
Si(2)   0.28970   0.17180   0.79990   1.00000   0.00469
Mg(1)   0.00000   0.08980   0.50000   1.00000   0.00646
Cr(2)   0.00000   0.17850   0.00000   0.38000   0.00431
Mg(2)   0.00000   0.17850   0.00000   0.62000   0.00431
Mg(3)   0.00000   0.00000   0.00000   1.00000   0.00481
Mg(4)   0.00000   0.27400   0.50000   0.05000   0.01710
Na(4)   0.00000   0.27400   0.50000   0.95000   0.01710
NaA   0.00000   0.50000   0.00000   0.27000   0.02520
NaA(m)   0.04020   0.50000   0.09460   0.09000   0.03014
NaA(2)   0.00000   0.47430   0.00000   0.08000   0.02812
Mg(4*)   0.00000   0.24410   0.50000   0.04000   0.00519
O1   0.11280   0.08590   0.21360   1.00000   0.00659
O2   0.11890   0.16780   0.73160   1.00000   0.00633
F3   0.10290   0.00000   0.70910   1.00000   0.00785
O4   0.36180   0.25100   0.79470   1.00000   0.01077
O5   0.35220   0.12940   0.08280   1.00000   0.00874
O6   0.34450   0.11880   0.58260   1.00000   0.00950
O7   0.34300   0.00000   0.29090   1.00000   0.00899