High pressure behaviour of tobermorite supergroup minerals: An in situ synchrotron X-ray powder diffraction study

Abstract The high-pressure behaviour of two natural samples of kenotobermorite [Ca4Si6O15(OH)2·5H2O] and clinotobermorite [Ca5Si6O17·5H2O] has been studied by in situ synchrotron X-ray powder diffraction. The samples were compressed in silicone oil using a diamond anvil cell. The calculated bulk moduli are as following: kenotobermorite K0 = 83.2 ± 0.4 GPa and clinotobermorite K0 = 93.5 ± 0.8 GPa. The presence of “zeolitic” Ca in clinotobermorite induces a lower compressibility in this sample. The comparison of the current results with previous studies evidenced that experimentally determined bulk moduli are generally higher than those obtained by theoretical calculations and the differences are related to the configuration of the silicate chains as well as to the content of “zeolitic” cations and H2O molecules.