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In one ear …︁ : The outer shape and inner architecture of individual particles of a complex calcite–gelatine composite resemble the known characteristics of biogenic otoconia (“ear dust”; see picture). The relationships between the morphology of artificial and biogenic specimens are discussed.

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Carbonated fluorapatite-gelatine nanocomposites were grown by the double-diffusion technique within a gelatine gel. The carbonate content was varied, whereas all other experimental parameters (Ca 2+ , [PO 4 ] 3-, Fconcentrations, gel concentration, pH, temperature, and growth time) were kept constant. The composite aggregates grown within so-called Liesegang bands were characterized by XRD, chemical analysis, FT-IR and Raman spectroscopy, TG/DTA/MS, SEM and TEM. In the carbonated fluorapatite-gelatine nanocomposites the carbonate ions replace the phosphate groups (so-called B-type substitution). Apart from the fact that the biomimetic nanocomposites contain carbonated fluorapatite as the inorganic component, the chemical composition of the aggregates is similar to that of biological hard tissues. The content of carbonate, sodium, and the organic component in the biomimetic composites is closest to that of dental enamel. The morphogenesis of the carbonated composites was investigated as a function of the carbonate concentration in the solutions (also reflected in the carbonate content of the composites). In general, the morphogenesis of the carbonated composite aggregates is closely related to that of pure fluorapatite-gelatine nanocomposites (form development from a seed via dumbbell states to a notched sphere). With increasing carbonate content, however, the aggregates become significantly rounded and compressed, an observation that clearly reflects the decreasing coherence length ([001] direction) of the nanosubunits assembling the composite structure.