We request 3 days of beam-time on ENGIN-X to investigate the influence of lattice preferred orientation on the onset of mechanical twinning in polycrystalline calcite (CaCO3) during high temperature, uniaxial compression. We would like to deform cores taken in three orthogonal directions from a sample with a moderately strong (by geological standards) texture to examine how changing the ease by which the precursory phenomenon of elastic twinning can occur influences both the elastic (recoverable) behaviour of the polycrystal, and the stress required for the onset of permanent twinning. The experiments form part of a larger research programme in which we are seeking to provide better experimental constraints on models that seek to specify the mechanical properties of polycrystalline materials from those of their constituent grains.