data_global
_chemical_name_mineral 'Gehlenite'
loop_
_publ_author_name
'Raaz F'
_journal_name_full 'Sitzungsberichte der Akademie der Wissenschaften in Wien'
_journal_volume 139 
_journal_year 1930
_journal_page_first 645
_journal_page_last 672
_publ_section_title
;
 Untersuchungen uber die Kristallstruktur von Sesquioxyden und Verbindungen ABO3
;
_database_code_amcsd 0017917
_chemical_formula_sum 'Ca2 Al2 Si O7'
_cell_length_a 7.69
_cell_length_b 7.69
_cell_length_c 5.1
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 301.594
_exptl_crystal_density_diffrn      3.019
_symmetry_space_group_name_H-M 'P -4 21 m'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '1/2-y,1/2-x,z'
  'y,-x,-z'
  '1/2-x,1/2+y,-z'
  '-x,-y,z'
  '1/2+y,1/2+x,z'
  '-y,x,-z'
  '1/2+x,1/2-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
Ca1   0.16000   0.34000   0.49000
Al1   0.35000   0.15000   0.05000
Si1   0.00000   0.00000   0.00000
O1   0.00000   0.50000  -0.19000
O2   0.35000   0.15000  -0.26000
O3   0.15000   0.09000   0.19000