The mechanisms by which calcium ions are transported through the fluorapatite lattice are investigated using computer simulations. Cation vacancy assisted pathways are considered and migration energy barriers are calculated using a nudged elastic band transition state search. Migration activation energies for a range of divalent cations, in addition to calcium are compared. Generally there is very little change in activation energy as cation radius increases. Furthermore, in all cases the lowest energy migration pathways occur parallel to the c-axis either associated with the central anion channel via Ca(2) sites or away from the channel and via Ca(1) sites.