Clay-hosted rare earth element (REE) deposits in Western Australia represent an emerging resource; however, most are non–ion-adsorption types and are refractory to conventional low intensity leaching. This study systematically evaluates physical, thermal, and thermochemical treatments to upgrade eight clay-hosted REE samples, where upgrading is defined as both increasing REE concentration and enhancing leachability. Mineralogical and chemical responses were evaluated using quantitative X-ray diffraction (QXRD), elemental assays, and leaching test results. Based on QXRD, samples were classified into two groups: Group I clays, categorised by crandallite-group minerals, and Group II clays, characterised by high K-feldspar content. Initial ammonium sulfate screening confirmed that all samples are refractory, necessitating pre-treatment prior to leaching. Physical upgrading by wet (