Tridacna derasa shells show a crossed lamellar microstructure consisting of three hierarchical lamellar structural orders. The mineral part is intimately intergrown with 0.9 wt% organics, namely polysaccharides, glycosylated and unglycosylated proteins and lipids, identified by Fourier transform infrared spectrometry. Transmission electron microscopy shows nanometre-sized grains with irregular grain boundaries and abundant voids. Twinning is observed across all spatial scales and results in a spread of the crystal orientation angles. Electron backscatter diffraction analysis shows a strong fibre texture with the  axes of aragonite aligned radially to the shell surface. The aragonitic  and  axes are oriented randomly around . The random orientation of anisotropic crystallographic directions in this plane reduces anisotropy of the Young’s modulus and adds to the optimization of mechanical properties of bivalve shells.
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- electron backscatter diffraction
- transmission electron microscopy
- Young’s modulus