We request 4 days of beam-time on ENGIN-X to measure the elastic behaviour of polycrystalline samples of gypsum, antigorite, and talc as a function of uniaxial load. All three are hydrous minerals that are of great significance in accounting for the mechanical behaviour of faults, with talc and antigorite assuming a particular prominence in recent thinking about processes of fault weakening. Our objectives are two-fold: (1) to establish the extent to which the neutron diffraction experiments we have been performing on ENGIN-X to characterize the elastic behaviour of anhydrous minerals can be extended to include geologically significant protonated materials, and (2) to improve our understanding of the elastic behaviour of talc and antigorite. This proposal utilises the experience gained in our March 2010 experiment which unfortunately was curtailed early due to ISIS running problems.