Conclusion
Apatites: naturally occurring phosphates

Although the basic structure of apatite was determined in 1930, many aspects of this family of compounds with remarkable but difficult-to-synthesize properties are still under discussion in the scientific world. The deceptive nature of apatites is well summed up by this comment from a chemical catalog marketing calcium orthophosphate Ca ₃ (PO ₄ ) ₂ : a marketed product obtained from bone ash, but also found in cookware deposits, in urinary calculi, a component of bone and dental prosthesis ceramics. Mineralogically, it corresponds to the mineral whitlockite.

It is also stated that there is some controversy as to whether calcium orthophosphate exists in amorphous form, and whether it transforms into hydroxyapatite or is a mixture...