The fate of fossil bone is shown to be governed by diagenesis reaction mechanisms which include: (1) disintegration of both main inorganic and organic components of bone texture; (2) ion exchange with the substituted carbonate-type apatite overlaying sinter phases, as well as with the soil surroundings and the atmosphere, and (3) decay of bones follows also from physical implications like bursting our of brushite from the osseous texture by increase in crystal volume. The organic matrix decomposes mostly by microbial action according to conditions of temperature and humidity. New results are given on interchange phases and stable end products of carbonated and Sr substitutes of the apatite series. Reactions of paracrystalline and amorphous compounds come up clearly also with the reactions and transformations in burnt bones.