between January and July 2025. The regression results indicated that the operation of the SK240 flash flotation cell had a statistically significant positive effect on both gold (1.062 ± 0.736) and copper (0.517 ± 0.285) recovery at the 90% confidence level, confirming that the recovery improvements observed during commissioning were sustained under normal operating conditions. Comparison of Regression Lines was performed by comparing regression lines of gold recovery versus gold feed grade for SK240 ON and OFF conditions. This evaluation detected a highly significant improvement in gold recovery when the SkimAir® was operating (P‑value = 8.43 × 10⁻¹⁰). The mean improvement in overall gold recovery was estimated at 1.99 ± 0.53% at the 90% confidence level. In addition, pulp chemistry surveys conducted by site personnel indicated improvements associated with SK240 operation, including more favourable pulp chemistry and reduced oxygen demand. These observations suggest that the presence of the SK240 may create conditions conducive to downstream sulphide flotation using xanthate collectors. The effect is likely linked to reduced ferric ion activity and enhanced dixanthogen stability within the pulp, promoting more selective sulphide mineral recovery. 5.2 Post-installation: Survey Following the successful installation and commissioning of the SK240 cell into the Ernest Henry Operations flotation circuit, a flotation survey was conducted to evaluate circuit performance during operation. Summary of the survey results is shown in Table 4. Table 4 – Survey results post-installation of SK240 cell Stream TPH Au Cu (g/t) Recovery (%) (%) Recovery (%) Rougher Feed 837.88 0.49 100 0.88 100 Rougher Concentrate 19.94 9.10 44.20 29.31 79.22 Scavenger Concentrate 91.18 2.03 1.44 SK240 Concentrate 3.93 34.78 33.35 21.58 11.51 Cleaner 3 Concentrate 22.66 9.00 49.68 27.40 84.16 Final Concentrate 26.59 12.81 83.03 26.54 95.67 Survey results indicated that the SK240 flash flotation cell recovered 74% of the gold and 65% of the copper reporting to the regrind circuit. Relative to pre‑installation performance, the SK240 substantially reduced the recirculation of valuable minerals within the regrind circuit, from 1750% prior to installation, the gold recirculating load has been reduced to 337% (based on the survey data), confirming the effectiveness of early recovery of liberated valuable particles. Table 5 presents the concentrate grades and associated recoveries from the post-installation survey and the simulation results from the previous section (4.2). Also shown in the table are the recoveries and grades for the Cleaner 3 concentrate and the final concentrate.
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