data_global
_chemical_name_mineral 'Cummingtonite'
loop_
_publ_author_name
'Fischer K F'
_journal_name_full 'American Mineralogist'
_journal_volume 51
_journal_year 1966
_journal_page_first 814
_journal_page_last 818
_publ_section_title
;
 A further refinement of the crystal structure of cummingtonite
 (Mg,Fe)7(Si4O11)2(OH)2
;
_database_code_amcsd 145
_chemical_formula_sum 'Si8 (Mg4.68 Fe2.32) O24'
_cell_length_a 9.51
_cell_length_b 18.19
_cell_length_c 5.33
_cell_angle_alpha 90.0
_cell_angle_beta 101.9
_cell_angle_gamma 90.0
_cell_volume 902.205
_exptl_crystal_density_diffrn  3.136
_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
Si1   0.2874  0.0842  0.2746  1.0  0.00456
Si2   0.2977  0.1688  0.7817  1.0  0.00545
Mg1   0.0  0.0872  0.5  0.84  0.00481
Fe1   0.0  0.0872  0.5  0.16  0.00481
Mg2   0.0  0.1773  0.0  0.95  0.00456
Fe2   0.0  0.1773  0.0  0.05  0.00456
Mg3   0.0  0.0  0.0  0.84  0.0038
Fe3   0.0  0.0  0.0  0.16  0.0038
Mg4   0.0  0.2597  0.5  0.13  0.01001
Fe4   0.0  0.2597  0.5  0.87  0.01001
O1   0.1135  0.0874  0.2087  1.0  0.00709
O2   0.1232  0.1721  0.7193  1.0  0.00849
O3   0.1134  0.0  0.7067  1.0  0.01026
O4   0.3798  0.246  0.7716  1.0  0.01127
O5   0.3514  0.131  0.0659  1.0  0.01127
O6   0.3488  0.1185  0.5597  1.0  0.01279
O7   0.3417  0.0  0.2719  1.0  0.01115