This dataset contains results of experiments to measure the relative strength of mid-ocean ridge basalt (MORB) and hartzbergite at pressures of the transition zone and lower mantle, along with the absolute rheology of the CF (calcium ferrite-type) phase under lower mantle conditions. Deformation experiments were conducted using: - The D-T Cup Press at University College London (UCL) - The D-111 Press at the Institute for Planetary Materials, Okayama University, Misasa, Japan; - The D-111 module of the SPEED Mk-II at SPring-8 synchrotron radiation facility, Japan The dataset includes: - Scanning electron microscope (SEM) images of recovered samples; - 2-D diffraction images of recovered samples to determine lattice preferred orientations (LPOs); - 2-D diffraction data collected at regular intervals during in-situ deformation experiments to determine differential stress in samples - Radiographic images of samples collected at regular intervals during in-situ deformation experiments to determine the length change of samples. These data provide measurements of rheology of transition-zone and lower-mantle rocks and minerals, supporting investigations of flow in the mantle transition zone and mechanisms of MORB segregation and ponding around the 660 km seismic discontinuity.