Lower Lead Recovery Highlights Processing Challenges at MTB’s Nxuu Deposit

Hydrometallurgical Advances at Nxuu

Mount Burgess Mining NL (ASX: MTB) has unveiled interim results from its latest hydrometallurgical test work on the Nxuu Deposit in Botswana, revealing significant progress in metal recovery rates. The test work, conducted in March 2025, focused on optimizing leaching kinetics by adjusting key process parameters such as pressure, temperature, and pH.

The standout outcome is a zinc recovery exceeding 96%, achieved through a dual leaching process combining alkaline and acid pressure leach tests. Vanadium recovery also impressed at 91.1%, alongside notable extraction rates for strategic metals germanium (77.3%) and gallium (59.3%). Lead recovery was recorded at 79.4%, somewhat lower than previous flotation test results which reached 93%, indicating room for further process refinement.

Strategic Implications and Next Steps

Chairman and Managing Director Nigel Forrester described the results as "highly encouraging," highlighting the deposit’s potential not only for base metals but also for rare earth elements (REEs) and other critical minerals. The hydrometallurgical approach could offer a more efficient and environmentally sensitive alternative to traditional flotation methods, particularly for the oxide-rich Nxuu orebody.

These metallurgical findings will feed directly into a scoping study planned for later in 2025, which aims to evaluate the economic viability and processing pathways for the deposit. The study will also consider the integration of by-product recoveries, including vanadium, gallium, germanium, and several REEs such as lanthanum, neodymium, praseodymium, cerium, samarium, and europium, with extraction rates ranging from 63% to over 90% for some elements.

Robust Technical Foundation

The announcement is accompanied by comprehensive JORC-compliant technical data detailing sampling techniques, drilling methods, assay procedures, and mineral resource estimation for both the Nxuu and Kihabe deposits. The mineral resources are classified as Indicated and Inferred, supported by close-spaced drilling and rigorous quality control protocols. The deposits lie within a 1000 sq km prospecting licence in northwestern Botswana, an area characterized by flat-lying quartz wacke units hosting sub-horizontal mineralisation.

Importantly, the test work and resource modelling benefit from extensive laboratory analysis by Intertek Genalysis and independent audits by Ashmore, ensuring data integrity and confidence in the geological interpretation. The company has also outlined plans for further metallurgical testing and infill drilling to enhance recovery rates and resource confidence.

Balancing Optimism with Caution

While the hydrometallurgical results mark a technical milestone, the lead recovery rate suggests that flotation remains a competitive process for certain metals. In addition, the economic assumptions underlying metal recoveries and mining methods remain preliminary. Environmental considerations and waste management strategies are yet to be fully developed, reflecting the early stage of project evaluation.

Nevertheless, the combination of high recoveries for multiple metals, including critical strategic elements, positions the Nxuu Deposit as a potentially valuable asset in the evolving landscape of base and strategic metals supply.