The process development phase of the redevelopment of the Hillgrove Gold–Antimony Project highlighted significant variability in flotation performance that could not be explained by conventional metallurgical test work alone. An integrated mineralogical and metallurgical investigation was undertaken to identify the fundamental controls on antimony and gold recovery and to define robust operating parameters for this complex, oxidation-prone sulfide system. Quantitative mineralogy showed that antimony is almost entirely hosted as stibnite, occurring in texturally complex aggregates with quartz, pyrite and gold across a broad grain size range. Gold deportment analysis revealed that nearly half of the gold is associated with stibnite, either as inclusions or as invisible gold, explaining the strong coupling between Au and Sb recovery and the limited effectiveness of reagent-based separation. Thin oxidation rims on fine stibnite particles were identified as a key constraint on flotation kinetics and ultimate recovery, particularly in partially oxidised material. Flotation testing demonstrated that liberation, oxidation state and gangue association govern metallurgical response. A primary grind size of P80 180 µm provided sufficient stibnite liberation while avoiding excessive fines generation, while controlled regrinding of the rougher concentrate significantly improved cleaner selectivity through liberation of ultrafine quartz. Collector comparisons showed that several reagents approached a mineralogically imposed recovery ceiling, confirming that recovery limits are controlled by oxidation rather than reagent inefficiency alone. Collectively, these findings demonstrate that integrating quantitative mineralogy with flotation test work shifts the role of mineralogy from post-hoc explanation towards a more predictive understanding of metallurgical performance, providing a stronger basis for flotation optimisation at the Hillgrove Gold–Antimony Project.