Powder XRD measurements of the Na-majorite and NaPx polymorphs of garnet and pyroxeneRaw diffraction data are provided as collected using unmonochromated Co radiation on the Analytical X'Pert Pro diffractometer in UCL Earth Sciences. Data are provides in xddml formats (as default saved in the diffractometer software) with no corrections or editing.Data supporting publication submitted to Physics and Chemistry of Minerals. Full description of data and processing to obtain results described in the text.