data_global _chemical_name_mineral 'Fluoro-eckermannite' loop_ _publ_author_name 'Oberti R' 'Hawthorne F C' 'Camara F' 'Raudsepp M' _journal_name_full 'American Mineralogist' _journal_volume 84 _journal_year 1999 _journal_page_first 102 _journal_page_last 111 _publ_section_title ; Unusual M3+ cations in synthetic amphiboles with nominal fluoro-eckermannite composition: Deviations from stoichiometry and structural effects of the cummingtonite component Sample: Sc, Na.92Na1.97Mg.03Mg3.95Sc1.05Si8O22F2 ; _database_code_amcsd 0002056 _chemical_formula_sum 'Si8 Mg4 Sc1.06 Na3.65 O22 F2' _cell_length_a 9.820 _cell_length_b 18.036 _cell_length_c 5.290 _cell_angle_alpha 90 _cell_angle_beta 103.64 _cell_angle_gamma 90 _cell_volume 910.506 _exptl_crystal_density_diffrn 3.077 _symmetry_space_group_name_H-M 'C 1 2/m 1' loop_ _space_group_symop_operation_xyz 'x,y,z' '1/2+x,1/2+y,z' 'x,-y,z' '1/2+x,1/2-y,z' '-x,y,-z' '1/2-x,1/2+y,-z' '-x,-y,-z' '1/2-x,1/2-y,-z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_occupancy _atom_site_U_iso_or_equiv Si(1) 0.28270 0.08450 0.29070 1.00000 0.00456 Si(2) 0.28830 0.16950 0.79530 1.00000 0.00545 Mg(1) 0.00000 0.08840 0.50000 1.00000 0.00646 Sc(2) 0.00000 0.18150 0.00000 0.53000 0.00608 Mg(2) 0.00000 0.18150 0.00000 0.47000 0.00608 Mg(3) 0.00000 0.00000 0.00000 1.00000 0.00646 Na(4) 0.00000 0.27600 0.50000 0.97000 0.02546 Mg(4) 0.00000 0.27600 0.50000 0.03000 0.02546 NaA 0.00000 0.50000 0.00000 0.27000 0.02546 NaA(m) 0.04070 0.50000 0.09370 0.52000 0.02951 NaA(2) 0.00000 0.47490 0.00000 0.20000 0.03888 O1 0.11410 0.08460 0.21600 1.00000 0.00595 O2 0.11940 0.16590 0.72650 1.00000 0.00621 F3 0.10120 0.00000 0.70970 1.00000 0.00747 O4 0.36000 0.24830 0.79680 1.00000 0.00988 O5 0.34900 0.12740 0.07830 1.00000 0.00925 O6 0.34450 0.11800 0.57890 1.00000 0.00912 O7 0.34270 0.00000 0.29070 1.00000 0.00899