data_global _chemical_name_mineral 'Olmsteadite' loop_ _publ_author_name 'Moore P B' 'Araki T' 'Kampf A R' 'Steele I M' _journal_name_full 'American Mineralogist' _journal_volume 61 _journal_year 1976 _journal_page_first 5 _journal_page_last 11 _publ_section_title ; Olmstaedite, K2Fe2[Fe2(Nb,Ta)2O4(H2O)4(PO4)4], a new species, its crystal structure and relation to vauxite and montgomeryite ; _database_code_amcsd 0000485 _chemical_formula_sum '(Nb.59 Ta.41) Fe2 K P2 O12 H4' _cell_length_a 7.512 _cell_length_b 10.000 _cell_length_c 6.492 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 487.679 _exptl_crystal_density_diffrn 3.662 _symmetry_space_group_name_H-M 'P b 21 m' loop_ _space_group_symop_operation_xyz 'x,y,z' '-x,1/2+y,z' 'x,y,-z' '-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 Nb 0.27254 0.73837 0.00000 0.59000 0.00557 Ta 0.27254 0.73837 0.00000 0.41000 0.00557 Fe 0.02061 0.00000 0.24183 1.00000 0.00975 K 0.53021 0.97416 0.50000 1.00000 0.03242 P1 0.18320 0.74120 0.50000 1.00000 0.00773 P2 0.32530 0.41490 0.00000 1.00000 0.00697 O1 0.08230 0.87290 0.50000 1.00000 0.01102 O2 0.06310 0.61920 0.50000 1.00000 0.02267 O3 0.30590 0.73760 0.30900 1.00000 0.01558 O4 0.41800 0.55470 0.00000 1.00000 0.01102 O5 0.47230 0.30670 0.00000 1.00000 0.01317 O6 0.21380 0.39780 0.19760 1.00000 0.01153 O7 0.15750 0.89990 0.00000 1.00000 0.01469 O8 0.07350 0.63170 0.00000 1.00000 0.01697 Wat 0.25240 0.11170 0.27200 1.00000 0.03192