Hi Joza,

You can get an interpretation initially from couple of papers from good journals. Here I can give one link (cross check other papers as well), which might be useful for you:

http://www.sciencedirect.com/science/article/pii/S0300571213001267

thanks

One important thing is that the concept of group frequencies can completely break down in case of inorganic materials. Actually this is the common case. Only if you have molecular entities like SO42- or PO43- you can find certain group frequencies. However, since the molecular symmetry may be altered due to the local symmetry in the crystal lattice, also the spectral pattern of these entities may be different.

Maybe you want to check the signalled paper, as it ascribes FTIR absorption bands for a layer containing poorly crystallised hydroxyapatite and octacalciumphosphate over phosphosilicate glasses: 

Article Network connectivity and bio-mineralization of 0.45SiO2–-(0....