Birch-Murnaghan Equation of State and High Pressure Compressibility of Halloysite

K0S and K0S, the zero pressure adiabatic bulk modulus and its first pressure derivative of Birch-Murnaghan EOS (isentrope) for halloysite, are obtained in terms of shock Hugoniot data by using the Eulerian finite strain theory. Under the assumption =0.43(0/), for the low pressure phase K0S=32.16 GPa and K0S=7.17, but we find K0S=103.28 GPa, K0S=4.97 and K0S=95.85 GPa, K0S=5.35 for the high pressure phase, with the phase transition energy of 579.1 and 1 000 J/g, respectively, under ＝1.0(0/)1.5. Analysis for the compressibility of its low-pressure phase, high-pressure phase and mixed-phase indicate that the different compressibilities between them corresponding to their different phase compositions.