Abstract Chemical and structural changes in bones and dentine from Cervus elaphus jaws during fossilization were studied by chemical analysis, infrared spectroscopy (IR) and X-ray diffraction (XRD). Data were used to discuss the modifications of bones and dentine from the Lazaret prehistoric cave (Nice, France) which is an important archeologic site of Middle Pleistocene age. Fossil bones and dentine mainly consisted of hydroxy-carbonate apatite as the primary phase and of calcite as a secondary phase. Carbonation, fluorination and recrystallization processes are shown as more important in bone and dentine than in tooth enamel. A good correlation was found between the a cell parameter of apatite and its CO 3 and fluorine contents in the bones studied. Fluorine enrichment seems to be related to the permeability of the upper sedimentary levels. Lazaret fossil bones and dentine are less stable than enamels and their use for dating has to be taken with caution.