data_global _chemical_name_mineral 'Cummingtonite' loop_ _publ_author_name 'Yang H' 'Hazen R M' 'Prewitt C T' 'Finger L W' 'Lu R' 'Hemley R J' _journal_name_full 'American Mineralogist' _journal_volume 83 _journal_year 1998 _journal_page_first 288 _journal_page_last 299 _publ_section_title ; High-pressure single-crystal X-ray diffraction and infrared spectroscopic studies of the C2/m-P2_1/m phase transition in cummingtonite Sample: P = 1.32 GPa ; _database_code_amcsd 0001973 _chemical_formula_sum 'Fe3.471 Mg3.445 Al.008 Ca.076 Si8 O24' _cell_length_a 9.4498 _cell_length_b 18.1083 _cell_length_c 5.2978 _cell_angle_alpha 90 _cell_angle_beta 102.417 _cell_angle_gamma 90 _cell_volume 885.353 _exptl_crystal_density_diffrn 3.337 _symmetry_space_group_name_H-M 'P 1 21/m 1' loop_ _space_group_symop_operation_xyz 'x,y,z' 'x,1/2-y,z' '-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_occupancy _atom_site_U_iso_or_equiv Fe1 -0.24580 0.33700 0.49380 0.40500 0.00836 Mg1 -0.24580 0.33700 0.49380 0.59500 0.00836 Fe2 -0.25210 0.42680 0.99400 0.20700 0.00925 Mg2 -0.25210 0.42680 0.99400 0.78900 0.00925 Al2 -0.25210 0.42680 0.99400 0.00400 0.00925 Fe3 -0.25160 0.25000 0.98950 0.39300 0.00811 Mg3 -0.25160 0.25000 0.98950 0.60700 0.00811 Fe4 -0.26040 0.50930 0.48410 0.92700 0.00988 Mg4 -0.26040 0.50930 0.48410 0.03500 0.00988 Ca4 -0.26040 0.50930 0.48410 0.03800 0.00988 Si1A 0.04300 0.33640 0.27680 1.00000 0.00760 Si1B 0.53520 0.83150 0.27680 1.00000 0.00646 Si2A 0.05160 0.41980 0.78080 1.00000 0.00823 Si2B 0.54530 0.91750 0.78470 1.00000 0.00937 O1A -0.13530 0.33950 0.21940 1.00000 0.00925 O1B 0.36830 0.83430 0.20220 1.00000 0.00836 O2A -0.12790 0.42530 0.71010 1.00000 0.00709 O2B 0.38110 0.91980 0.73150 1.00000 0.00785 O3A -0.11760 0.25000 0.72160 1.00000 0.00963 O3B 0.35740 0.75000 0.69850 1.00000 0.00836 O4A 0.13270 0.49610 0.77010 1.00000 0.01406 O4B 0.62620 0.99530 0.76390 1.00000 0.01507 O5A 0.10590 0.37740 0.04630 1.00000 0.00874 O5B 0.59760 0.88620 0.08330 1.00000 0.00950 O6A 0.10250 0.37440 0.54890 1.00000 0.01178 O6B 0.60650 0.86150 0.57960 1.00000 0.01368 O7A 0.09090 0.25000 0.28800 1.00000 0.00811 O7B 0.60270 0.75000 0.25260 1.00000 0.00684