Rubidium (Rb) is a reactive alkali critical metal experiencing increasing demand due to its high-tech applications in precision atomic clocks and emerging quantum computing technologies. Historically, Rb has been sourced primarily from Lithium-Caesium-Tantalum (LCT) pegmatites, where it is recovered as a by-product of lithium (Li) and caesium (Cs) extraction. Its enrichment is linked to the extreme differentiation of peraluminous granitic melts, during which incompatible elements are progressively concentrated in residual melts and fluids. However, despite its critical importance, the geological processes responsible for extreme Rb enrichment in pegmatite systems remain poorly understood. In this study, the authors investigated the mechanisms controlling unique high Rb concentrations within the Mount Edon LCT pegmatite system in Western Australia. By focusing on Rb-enriched mineral phases, including K-feldspar and the mica group minerals, this research investigated the geochemical correlations between Rb and associated elements eg Cs, potassium (K), Li, and fluorine (F). The authors used a multi-analytical approach that goes beyond conventional whole-rock composition methods by integrating microscopic-scale techniques (eg optical microscopy, automated mineralogy, and mass spectrometry analyses) to characterise mineral-scale textures and quantify in situ trace element distributions that will support the Rb recovery process. The strong partitioning of Rb into lepidolite highlights mica-rich zones as the most promising targets for both Rb (~3.5 wt per cent) and Cs (~0.9 wt per cent), supporting more selective extraction strategies. Nevertheless, K-feldspar exhibits Rb concentrations with ~0.7 wt per cent, comparable to those of muscovite, suggesting an alternative extraction pathway with fewer interfering ions. This study establishes a mineralogical–geochemical framework to define Rb hosts, quantify element deportment, and link grain-scale distribution to processing behaviour. The integrated analytical approach constrains metallurgical strategies, providing transferable insights for optimising Rb and Cs recovery from LCT pegmatites globally, beyond Mount Edon, and enhancing the economic potential of critical metal resources.