Steam Engine Gold Recovery Hits Up to 91% with Gravity Circuit Addition

Context and Objectives

Superior Resources Limited (ASX – SPQ) has released positive results from its recent coarse-grind metallurgical test program on the 100%-owned Steam Engine Gold Project in northeast Queensland. The program aimed to assess the impact of coarser grinding on gold recovery and evaluate the benefits of incorporating gravity concentration into processing. These tests build on extensive prior metallurgical work and are integral to advancing the project’s development pathway.

Key Findings on Grind Size and Recovery

The test work compared gold recoveries at a coarser grind size of 150 microns against the standard finer grind of 75 microns. As expected, coarser grinding resulted in a modest reduction in recovery, approximately 6% lower for the Steam Engine Lode and around 2% for the Eastern Ridge Lode. This aligns with metallurgical principles where finer grinding liberates more gold particles, enhancing recovery.

Despite this decrease, the coarse grind recoveries remain robust, averaging between 78% and 81.2% for the Steam Engine Lode and 91.4% for the Eastern Ridge Lode. These figures are consistent with previous test results and confirm the deposit’s favorable metallurgical characteristics.

Gravity Concentration Enhances Recovery

Importantly, the addition of a gravity concentration stage, using a Knelson Concentrator, demonstrated a significant uplift in overall gold recovery, boosting it by up to 8.3%. Gravity circuits are particularly effective at recovering free gold particles before cyanide leaching, improving process efficiency and potentially reducing reagent consumption.

The benefit of gravity concentration is more pronounced at coarser grind sizes, as finer grinding tends to liberate more gold for cyanide leaching alone. This insight will be critical in designing the optimal processing flowsheet, especially if the project moves towards an owner-operated plant scenario.

Financial Implications and Project Outlook

Superior’s Managing Director, Peter Hwang, highlighted that these metallurgical results support the positive outcomes of the recent Scoping Study, which assumed a base-case gold price of A$3,250 per ounce. At a higher assumed gold price of A$4,250 per ounce, the study’s financial model forecasts a pre-tax cash flow of approximately A$98 million, underscoring the project’s economic potential.

The test results also facilitate ongoing discussions with third-party toll treatment operators, a key step in advancing the project without immediate capital expenditure on processing infrastructure. However, the company notes that finer grinding could further improve recoveries, particularly in an owner-operated plant, albeit with potential trade-offs in operating costs and throughput.

Next Steps in Development

Looking ahead, Superior plans to conduct additional metallurgical studies as part of the Feasibility Study process. These will focus on refining processing parameters, pit optimisation, geotechnical assessments, and economic evaluations to determine the most efficient and cost-effective development strategy.

The company’s dominant land position in the Greenvale region, combined with its portfolio of high-grade copper-gold-silver and porphyry discoveries, positions it well for further exploration and value creation.