Rare-Earth Elements (REE) are critical minerals due to their role in high-performance magnets for renewable energy, electric vehicles, and defence, as well as associated geopolitical risks. Clay- hosted REE deposits are particularly attractive for exploration as they can contain substantial tonnages and can be extracted using weak acid (pH>4). This study provides a multiscale mineralogical characterisation of two clay-hosted REE projects in south-west Western australia: Splinter Rock and Balladonia, located ~80 km apart. These deposits are hosted within the albany- Fraser Orogen and associated with granites, gneisses, and granitoids of the Recherche and Esperance Supersuites, including the REE-enriched Booanya Granite. The region is overlain by Eucla Basin sediments and palaeovalleys, with bedrock and saprock exposed in elevated areas. Regolith-hosted REE enrichment extends across an area of 12 000 km2 and does not exhibit a stratigraphic control at a regional scale. Spectra-based mineralogy and geochemical analyses from drilling data were used to delineate boundaries between transported regolith, in situ saprolite and saprock. Detailed mineralogical investigations on selected drill holes included continuous infrared reflectance spectra collection using HyLogger-3 system to define analysis intervals for bulk and clay X-ray diffraction, scanning electron microscopy, and SEM-based automated mineralogy. Lithological boundaries between transported cover and in situ regolith were defined using bound water, and albedo IR reflectance spectra indices, while the saprolite and saprock contact can be identified by a sharp increase in potassium content. These results show that major lithological boundaries can be defined using both core scanning and handheld devices and provide a rapid workflow for resource domaining and sampling. The REE mineralogy is primarily hosted by secondary REE minerals, mainly monazite/rhabdophane, with local occurrences of bastnasite and allanite. The thickness of the REE mineralisation correlates with deposition sites of the Eucla basin palaeovalleys and can be used as a regional exploration tool.