Phosphate Minerals in Human Tissues

The mineralized or calcified tissues in biological systems are composed of two phases: organic and inorganic or mineral phases. In the invertebrates (e.g., echinoderms, mollusks, arthropods, etc.), the inorganic phase is usually calcium carbonate, CaCO3, predominantly in the form of either calcite or aragonite or both. In the invertebrates, the inorganic phase consists of one or more types of phosphate minerals (predominantly calcium phosphates) depending on the nature of calcification, i.e., normal (e.g., bones and teeth) or abnormal or pathological (e.g., dental calculi, salivary and urinary stones, soft tissue calcifications, etc.). In several pathologically calcified tissues, the mineral is non-phosphatic, such as calcium oxalates (whewellite and weddellite), sodium urates, uric acid, cysteine.