data_global
_chemical_name_mineral 'Beryl'
loop_
_publ_author_name
'Gibbs G V'
'Breck D W'
'Meagher E P'
_journal_name_full 'Lithos'
_journal_volume 1 
_journal_year 1968
_journal_page_first 275
_journal_page_last 285
_publ_section_title
;
 Structural refinement of hydrous and anhydrous synthetic beryl,
 Al2(Be3Si6)O18 and emerald, Al1.9Cr0.1(Be3Si6)O18
 Note: anhydrous emerald
;
_database_code_amcsd 0019468
_chemical_compound_source 'Synthetic'
_chemical_formula_sum '(Al1.9 Cr.1) Be3 Si6 O18'
_cell_length_a 9.219
_cell_length_b 9.219
_cell_length_c 9.198
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 120
_cell_volume 677.005
_exptl_crystal_density_diffrn      2.649
_symmetry_space_group_name_H-M 'P 6/m c c'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '-x,-x+y,1/2+z'
  'x,x-y,1/2-z'
  '-x+y,-x,-z'
  'x-y,x,z'
  '-y,-x,1/2+z'
  'y,x,1/2-z'
  'y,-x+y,-z'
  '-y,x-y,z'
  'x-y,-y,1/2+z'
  '-x+y,y,1/2-z'
  'x,y,-z'
  '-x,-y,z'
  'x,x-y,1/2+z'
  '-x,-x+y,1/2-z'
  'x-y,x,-z'
  '-x+y,-x,z'
  'y,x,1/2+z'
  '-y,-x,1/2-z'
  '-y,x-y,-z'
  'y,-x+y,z'
  '-x+y,y,1/2+z'
  'x-y,-y,1/2-z'
  '-x,-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
Al   0.66667   0.33333   0.25000   0.95000   0.00545
Cr   0.66667   0.33333   0.25000   0.05000   0.00545
Be   0.50000   0.00000   0.25000   1.00000   0.00291
Si   0.38750   0.11600   0.00000   1.00000   0.00139
O1   0.31200   0.23730   0.00000   1.00000   0.00481
O2   0.49930   0.14560   0.14500   1.00000   0.00342