Abstract: A biocompatible glass ceramic consisting of a vitreous matrix containing vitreous inclusions in which are dispersed crystals of a compound, isomorphous with hydroxyapatite, of at least the following elements: calcium, a lanthanide or yttrium, silicon, phosphorus and oxygen, these inclusions being surrounded by crystals of at least one compound belonging to the group consisting of Na.sub.2 Ca.sub.2 Si.sub.3 O.sub.9 and Ca.sub.3 (PO.sub.4).sub.2.2 Ca.sub.2 SiO.sub.4, can be used to construct artificial bone segments etc in bone surgery and bonds firmly with the new bone tissue without causing inflammation.