data_global
_chemical_name_mineral 'Bertrandite'
loop_
_publ_author_name
'Hazen R M'
'Au A Y'
_journal_name_full 'Physics and Chemistry of Minerals'
_journal_volume 13 
_journal_year 1986
_journal_page_first 69
_journal_page_last 78
_publ_section_title
;
 High-pressure crystal chemistry of phenakite (Be2SiO4)
 and bertrandite (Be4Si2O7(OH)2)
 Sample: P = 23 kbar
 Note: x-coordinate of O2 altered
;
_database_code_amcsd 0007376
_chemical_formula_sum 'Be4 Si2 O9 H2'
_cell_length_a 8.641
_cell_length_b 15.051
_cell_length_c 4.5338
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 589.646
_exptl_crystal_density_diffrn      2.684
_symmetry_space_group_name_H-M 'C m c 21'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '1/2+x,1/2+y,z'
  'x,-y,1/2+z'
  '1/2+x,1/2-y,1/2+z'
  '-x,y,z'
  '1/2-x,1/2+y,z'
  '-x,-y,1/2+z'
  '1/2-x,1/2-y,1/2+z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_U_iso_or_equiv
Be1   0.16790   0.05360   0.09400   0.00760
Be2   0.32460   0.22140   0.06100   0.00076
Si   0.32610   0.11350   0.65460   0.00659
O1   0.29390   0.12460   0.00000   0.01013
O2   0.20670   0.04380   0.49870   0.01267
O3   0.29480   0.20810   0.49040   0.01140
O4   0.00000   0.58210   0.58430   0.01140
O-H1   0.00000   0.76000   0.08260   0.01102
O-H2   0.00000   0.09160   0.07600   0.00760