STABILIZATION OF AMORPHOUS CALCIUM-CARBONATE BY SPECIALIZED MACROMOLECULES IN BIOLOGICAL AND SYNTHETIC PRECIPITATES

Communication: Composite structures in which amorphous and crystalline phases coexist are formed by some organisms. The spicules of the spon ge Clathrina are shown to be composed of a crystalline calcitic core a nd an outer layer of amorphous CaCO3 (see figure). The latter material , normally a highly unstable mineral, is stabilized in vitro by macrom olecules extracted from the outer sponge spicule layer. The combinatio n of crystalline and stabilized amorphous phases may have important im plications for materials applications.