Fluorapatite Hughes J M, Cameron M, Crowley K D American Mineralogist 76 (1991) 1857-1862 Ordering of divalent cations in the apatite structure: Crystal structure refinements of natural Mn- and Sr-bearing apatite sample Sr.29 _database_code_amcsd 0001422 9.3786 9.3786 6.8922 90 90 120 P6_3/m atom x y z occ Biso Ca1 2/3 1/3 .00092 .998 .732 Sr1 2/3 1/3 .00092 .002 .732 Ca2 -.00788 .24114 .25 .952 .670 Sr2 -.00788 .24114 .25 .048 .670 P .36899 .39827 .25 .51 O1 .4852 .3272 .25 .90 O2 .4670 .5879 .25 .98 O3 .25737 .3418 .0706 1.16 F 0 0 .25 .890 1.93