Pressure derivatives of the sound velocities of polycrystalline forsterite, with 6% porosity

The determination of the sound velocities of polycrystalline forsterite under pressure has been an important objective of our laboratory at Lamont. We have obtained numerous polycrystalline samples prepared in several laboratories and, until recently, have not been able to pass ultrasound through them. We finally obtained a sample of forsterite that yielded some weak echoes at 20 mhz, a barely marginal condition for measuring the elastic constants. We were able to determine the pressure derivatives of the sound velocities on this sample.