Compressibility of a natural kyanite to 17.5 GPa

The compressional behaviour of a natural kyanite, (Al1.99Fe0.01)SiO5, has been investigated to about 17.5 GPa at 300 K using a diamond-anvil cell and synchrotron X-ray diffraction. The pressure–volume data fitted to the third-order Birch–Murnaghan equation of state (EoS) yield an isothermal bulk modulus (K0T) of 192 ± 6 GPa and pressure derivative (K0T′) of 6 ± 1. When K0T′ is fixed as 4, the derived K0T is 201 ± 2 GPa. These values are in excellent agreement with most experimental determinations in the literature. Consequently, it can be concluded that the compressibility of kyanite under high pressures has been accurately constrained.