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 0000045 _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 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 1595.310 _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 0.00000 0.00000 0.77000 MgY 0.13300 0.06650 0.25500 AlZ 0.05000 0.36700 0.82500 SiT 0.19200 0.19200 0.62400 B 0.11700 0.23400 0.00000 O-H1 0.00000 0.00000 0.40300 O2 0.05800 0.11600 0.00000 O-H3 0.23300 0.11650 0.03200 O4 0.14200 0.07100 0.62400 O5 0.10200 0.20400 0.74200 O6 0.20000 0.20000 0.40300 O7 0.27900 0.24600 0.75800 O8 0.05800 0.29200 0.00000