Abstract: The microstructures of nacre layers in H. cumingii Lea Shells and freshwater pearls were investigated extensively via SEM and optical microscope. The results show that besides the normal laminate nacre layers, there are several special structures in H. cumingii Lea Shells, including columnar nacre, needle-like crystals layer and prism crystals layer. In columnar nacre, the thickness of a single aragonite tablet is 1μm, twice more than the thickness of aragonite tablet in normal nacre. However, these special structures are not found in nacre layers of normal freshwater pearls, which has shining surface. The nacre growth in freshwater pearls occurrs in a closed micro-environment of mantle sacs resulting in a uniform structure of nacre layers. The nacreous biocoatings were biofabricated on titanium implants using cylinder mantle sacs and were analysed by optical microscope and X-ray photograph. The results show that the nacreous biocoatings grow along the surface of the titanium implants.

Key words: nacre, microstructure, columnar nacre, nacreous coating