Abstract Several difficulties arise when studying the mineral component of calcified tissues: this material is complex, due to the large number of atomic components; it is poorly crystallized, heterogeneous, and varies with different factors (animal species, kind of bone, age, sampling zone, etc.); it is strongly linked to the organic component (collagen, etc.), and today no available technique allows a complete separation of these two components without alteration of one of the other. Research on synthetic materials allows the elaboration of some models to account, at least partially, for the nature and properties of the calcified-tissue mineral component. So, glycine fixation by apatite constitutes the first model of the collagen-apatite bond. The introduction of carbonate ions into the apatitic lattice can take place in two kinds of site, and under different forms. The replacement of PO 3- 4 ions by HPO 2- 4 can also be observed. The properties of phosphates depend on the presence of these various substituents, and therefore such substitutions can play an important role in phosphate behaviour in biological media. The study of the hydrolysis and crystallization of amorphous phosphate into apatite leads to new conceptions relative to the possible existence of an amorphous “phase” in calcified tissues. The conversion of amorphous phosphates to crystalline apatite is dependent on numerous ions (Mg 2+, P 2O 4- 7, CO 3 2-, etc.). Studies on synthetic materials can be regarded as a basis for the further study of calcified tissues, partic ularly to determine their constitution and properties. Besides, such studies enable the synthesis of materials, for implants, very similar to calcified tissues.