Shock compression and isentropic release of granite

New equation of state data for a weathered granite shocked to about 125 GPa are reported and combined with the Westerly granite data of McQueen, Marsh & Fritz (1967). The shock velocity (U_s)‐particle velocity (U_p) relations can be fitted with two linear regressions: U_s= 4.40 + 0.6U_p for a range of U_p up to about 2 km s^‐1 and U_s= 2.66 + 1.49U_p for a range of about 2 to 5 km s^‐1. The third‐order Birch‐Murnaghan equation of state parameters are K_os= 51‐57 GPa and K'_os= 1.4‐1.8 for the low‐pressure regime and K_os= 251 ± 30 GPa and an assumed K'_os= 4 for the high‐pressure regime. Compressive waveforms in dry and water‐saturated granite were measured at 10‐15 GPa using the VISAR technique. The measured wave profiles were successfully modelled using a Maxwellian stress‐relaxation material model. Water‐saturated granite is characterized by a ˜25 per cent lower yield strength and a ˜75 per cent longer material relaxation time than dry granite.