carbonate-apatite

CONT: Carbonate apatites are the most perplexing members of the apatite group from the standpoint of both chemistry and structure. Not only do they have CO[subscript 3] groups substituting for PO[subscript 4] groups, but they usually show an excess of water above F + OH = 2. ... Francolite is the F-bearing mineral of the carbonate apatites.
CONT: The mineralogy of phosphate deposits is usually complex, as they consist of a fine-grained mixture of various calcium phosphates, of which hydroxyl-apatite, carbonate-apatite, fluor-apatite ... are perhaps the most important.