data_global _chemical_name_mineral 'Nacrite' loop_ _publ_author_name 'Gruner J' _journal_name_full 'Zeitschrift fur Kristallographie' _journal_volume 85 _journal_year 1933 _journal_page_first 345 _journal_page_last 354 _publ_section_title ; The crystal structure of Nacrite and a comparison of certain optical properties of the caolin group with its structures _cod_database_code 1011080 ; _database_code_amcsd 0017977 _chemical_formula_sum 'Al2 Si2 O9' _cell_length_a 5.16 _cell_length_b 8.93 _cell_length_c 28.659990000 _cell_angle_alpha 90 _cell_angle_beta 91.72 _cell_angle_gamma 90 _cell_volume 1320.023 _exptl_crystal_density_diffrn 2.557 _symmetry_space_group_name_H-M 'C 1 c 1' 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' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z Al1 -0.25000 0.33330 0.00000 Al2 -0.25000 0.00000 0.00000 Al3 0.08330 0.00000 0.25000 Al4 0.08330 -0.33330 0.25000 Si1 0.43060 0.33330 0.09380 Si2 0.43060 0.00000 0.09400 Si3 0.43060 -0.33330 0.34380 Si4 0.43060 0.00000 0.34380 O1 -0.07780 0.50000 0.03819 O2 -0.07780 -0.16670 0.03819 O3 0.43610 0.16670 0.11460 O4 0.18610 0.41670 0.11460 O5 0.18610 -0.08330 0.11460 O6 -0.07780 -0.50000 0.28820 O7 -0.07780 0.16670 0.28820 O8 0.43610 -0.16670 0.36460 O9 0.18610 -0.41670 0.36460 O10 0.18610 0.08330 0.36460 O11 -0.07780 0.16670 0.03819 O12 -0.25560 -0.33330 0.21190 O13 -0.25560 0.00000 0.21190 O14 -0.25560 0.33330 0.21190 O15 -0.07780 -0.16700 0.28820 O16 0.07780 -0.33330 0.46180 O17 0.07780 0.00000 0.46180 O18 0.07780 0.33330 0.46180