Osteogenic compositions composed of a coprecipitate that contains at least one insoluble calcium salt and at least one complex between an osteogenic protein and a polysaccharide, the coprecipitate being in divided form, are described. Kits are also described, as are a process for preparing the coprecipitate in divided form, containing at least one insoluble calcium salt and at least one complex between an osteogenic protein and a polysaccharide.