data_global _chemical_name_mineral 'Topaz' loop_ _publ_author_name 'Northrup P A' 'Leinenweber K' 'Parise J B' _journal_name_full 'American Mineralogist' _journal_volume 79 _journal_year 1994 _journal_page_first 401 _journal_page_last 404 _publ_section_title ; The location of H in the high-pressure synthetic Al2SiO4(OH)2 topaz analogue Sample fluor-topaz from a Mexican rhyolite ; _database_code_amcsd 0001642 _chemical_formula_sum 'Al2 Si O4 F2' _cell_length_a 4.652 _cell_length_b 8.801 _cell_length_c 8.404 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 344.079 _exptl_crystal_density_diffrn 3.553 _symmetry_space_group_name_H-M 'P b n m' loop_ _space_group_symop_operation_xyz 'x,y,z' 'x,y,1/2-z' '-x,-y,1/2+z' '1/2+x,1/2-y,1/2+z' '1/2-x,1/2+y,1/2-z' '1/2-x,1/2+y,z' '1/2+x,1/2-y,-z' '-x,-y,-z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv Al 0.90303 0.13090 0.08283 0.00431 Si 0.39723 0.94035 0.25000 0.00367 O1 0.70360 0.03210 0.25000 0.00481 O2 0.45770 0.75600 0.25000 0.00494 O3 0.21020 0.98920 0.09240 0.00469 F 0.59820 0.25250 0.05610 0.00659