The Micro/Nanostructure Characteristics and the Mechanical Properties of Hemifusus tuba Conch Shell

The mollusk shell mobilizes calcium from environment for skeletal mineralization. This occurs through synthesizing solids in solution in the presence of organic molecules of specific interior regions of the conch shell. The ultrastructure and microhardness of the Hemifusus tuba conch shell living in the Huang/Bo sea area are investigated in the paper. It is shown that the composition and microstructure of the mollusk shell vary in different positions. The prodissoconch shell consists only of aragonite with the crossed-lamellar microstructure. While the spiral shell and the body shell of the Hemifusus tuba conch shell are composed of one calcite layer and several aragonite layers. The calcite layer consists of cylindrical grains, but the aragonite layers are crossed-lamellar ultrastructure at three size scales. The minimum structure size (the third-order lamella) is at about 20 nm − 80 nm. The margin of shell aperture is only composed of calcite with cylindrical grains. This natural optimization of the shell microstructure is intimately due to the growth of the organic matrix. At different positions the microhardness of mollusc shell is different due to different crystal structures and crystal arrangements. The growth process of shells allows a constant renewal of the material, thus enabling their functional adaptation to external environments.