Hydroxylapatite Wilson R M, Elliot J C, Dowker S E P American Mineralogist 84 (1999) 1406-1414 Rietveld refinement of the crystallographic structure of human dental enamel apatites Sample: Prep.63b, synthetic _database_code_amcsd 0002284 9.4232 9.4232 6.8833 90 90 120 P6_3/m atom x y z occ Ca1 2/3 1/3 .0014 Ca2 .2469 .9931 .25 P .3984 .3679 .25 O1 .3273 .4848 .25 O2 .5852 .4635 .25 O3 .3415 .2565 .0690 OH 0 0 .1917 .5 H 0 0 .0608 .5