In this work, we review the leaching behaviour of rare earth elements (REEs) from ores with variable ionic character and highlight the influence of mineralogy on the processing strategy and terminal REE recovery levels. As the grades of ion-adsorption ores are low, the recovery of REEs must be maximized to justify the economic process, while ensuring minimum environmental impact. Differing from the traditional ionic clays that primarily exhibit physisorption, samples in this study contained around 30% clay material and had varying degrees of REE partitioning via physisorption and mineralization (in both acid soluble and refractory phases). This chapter presents insights gained by processing the clays by ion-exchange leaching (IXL) using various lixiviants and by acid leaching to identify the optimum REE recovery route. Some of the ores contained up to 60% of adsorbed REEs that could be easily recovered by IXL, while in some other cases, the REEs were mainly associated with mineral phases, thus requiring strong acid leaching. This research reveals the connection between the mineral makeup and REE leaching behaviour in a non-standard ionic clay samples and highlights the need to consider different processing routes to optimize REE recovery.