Ultrasonic investigation of Aragonite elastic constants: natural mineral vs mollusk shell biomineral

The MHz-range ultrasonic pulse-echo technique was used to measure the longitudinal and shear sound velocities for different cuts of natural mineral Aragonite and of the nacre of Nautilus pompilius shell followed by the extraction of the elastic constants for both materials. On average, elastic stiffnesses of the biogenic shell aragonite were about 30% lower compared to the mineral. For constants related to BAW polarization along Z-direction, the difference was even larger than 50%, going along with strong acoustic attenuation. Laser Doppler vibrometer (LDV) measurements on both types of samples revealed a strongly different vibration behavior depending on the microstructure of the mineral and the shell samples.Additionally, two-dimensional bulk acoustic wave (BAW) field distributions were measured on both types of samples by means of Laser Doppler vibrometry (LDV)