data_global _chemical_name_mineral 'Dravite' loop_ _publ_author_name 'Hamburger G E' 'Buerger M J' _journal_name_full 'American Mineralogist' _journal_volume 33 _journal_year 1948 _journal_page_first 532 _journal_page_last 540 _publ_section_title ; The structure of tourmaline ; _database_code_amcsd 45 _chemical_compound_source 'de Kalb, New York, USA' _chemical_formula_sum 'Na Mg3 Al6 Si6 B3 (O31 H4)' _cell_length_a 15.951 _cell_length_b 15.951 _cell_length_c 7.24 _cell_angle_alpha 90.0 _cell_angle_beta 90.0 _cell_angle_gamma 120.0 _cell_volume 1595.31 _exptl_crystal_density_diffrn 2.994 _symmetry_space_group_name_H-M 'R 3 m' loop_ _space_group_symop_operation_xyz 'x,y,z' '2/3+x,1/3+y,1/3+z' '1/3+x,2/3+y,2/3+z' 'x,x-y,z' '2/3+x,1/3+x-y,1/3+z' '1/3+x,2/3+x-y,2/3+z' '-y,-x,z' '2/3-y,1/3-x,1/3+z' '1/3-y,2/3-x,2/3+z' '-x+y,y,z' '2/3-x+y,1/3+y,1/3+z' '1/3-x+y,2/3+y,2/3+z' '-y,x-y,z' '2/3-y,1/3+x-y,1/3+z' '1/3-y,2/3+x-y,2/3+z' '-x+y,-x,z' '2/3-x+y,1/3-x,1/3+z' '1/3-x+y,2/3-x,2/3+z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z NaX 0.0 0.0 0.77 MgY 0.133 0.0665 0.255 AlZ 0.05 0.367 0.825 SiT 0.192 0.192 0.624 B 0.117 0.234 0.0 O-H1 0.0 0.0 0.403 O2 0.058 0.116 0.0 O-H3 0.233 0.1165 0.032 O4 0.142 0.071 0.624 O5 0.102 0.204 0.742 O6 0.2 0.2 0.403 O7 0.279 0.246 0.758 O8 0.058 0.292 0.0