814 underloaded while cheaper upstream or downstream units become the constraint. The most competent ores are likely to enter the SAG mill at coarser sizes, and it is these ores that may benefit from more aggressive blasting. Conversely, softer ores do not require such blast intensification. The objective is to tailor blast designs to ore competency: producing finer fragmentation for the hardest materials to alleviate SAG mill constraints, while allowing coarser fragmentation for softer materials that can sustain higher mill fillings and power draw. In all cases, the goal is to maximize SAG mill power consumption. Achieving this level of integration relies heavily on the ability to identify the hardest and softest ores in advance, which in turn depends on an effective and reliable ore characterisation methodology. 1.1 SAG Milling Operation Effective Mine-to-Mill process integration requires a clear understanding of how the comminution circuit responds to both ore competency and blast fragmentation. This, in turn, demands a solid grasp of the fundamental operating principles of SAG mills. Unlike ball mills, SAG mills are equipped with a grate discharge mechanism, meaning that particles can only exit the mill once they are small enough to pass through the discharge grates. This feature imposes both a classification function and a finite discharge capacity on the mill. Two primary breakage mechanisms operate within a SAG mill (Napier-Munn et al., 1996), as illustrated in Error! Reference source not found.: high-energy impact breakage, which occurs through a limited number of events, and low-energy abrasion breakage, which occurs through a very large number of events and is the dominant source of fines generation. High SAG mill fillings favour abrasion breakage at the expense of impact breakage, whereas low mill fillings promote impact breakage at the expense of abrasion. Harder and coarser materials typically experience longer residence times within the SAG mill, leading to increased mill filling, higher power draw, constrained throughput, and finer final grind sizes. Conversely, softer and finer materials have shorter residence times, resulting in lower mill fillings and power draw, but enabling higher throughputs and coarser final grind sizes. Residence time is therefore a key determinant of fines generation: longer residence times increase exposure to abrasion breakage, producing more fines and reducing the workload transferred to downstream ball milling. As a consequence, SAG mill power draw naturally increases when processing harder and coarser ores and decreases when processing softer and finer ores. Figure 58 illustrates the performance of a 38-foot
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