Netta Vidavsky

Heinz A. Lowenstam's discovery in 1967, together with Ken Towe that the magnetite mineral in mature chiton teeth forms from a disordered transient precursor phase, ferrihydrite, remained an isolated curiosity for 30 years. During the last 15 years, many more examples were found in both invertebrates and vertebrates, where the mature crystalline mineral phase is formed through a transient amorphous precursor phase. Here we review this widespread phenomenon, and also describe the details of the transformation process in the formation of the calcitic spicules of the sea urchin larva.We identify many open questions.