• Favourable rare earth oxide leach extractions achieved using weak sulphuric acid at pH 2.0-2.5
• Potential to reduce iron impurities in heap leach liquor through extended residence time
• Optimum leach conditions identified for weathered and transitional granite ores

Red Metal Ltd has completed pH optimisation leach tests on samples from the Sybella rare earth deposit, highlighting the potential for low-cost heap leach processing. The tests on weathered and transitional granite ores from the Kary Zone achieved favourable rare earth oxide extractions using ambient temperature sulphuric acid at pH 2.0 to pH 2.5, which are weaker and lower-cost acid set points than previously indicated. The research also successfully demonstrated that weakening the acid strength over time leads to a step-change reduction in iron impurities while still maintaining strong rare earth extractions. This iron precipitation reaction is acid generating, allowing rare earth extractions to be maintained and acid addition to be reduced. The optimum leach conditions were identified as pH 2.0 for the weathered granite (0-12m) and pH 2.0-2.5 for the transitional granite (12-24m), with moderate acid consumption rates of 17 kg/t and 12 kg/t respectively, and low aluminium and iron impurity extractions. These new results have significantly improved on past test work and provide clear guidance for the upcoming column leach tests and future studies. The pending column leach results will provide more definitive data to support early-stage mine scoping for this unique, granite-hosted rare earth deposit.

The company looks forward to commencing column leach test work in the coming months to provide definitive data on crushed rock that better simulates a heap leach setting. Additional bottle roll tests on the Templeton Zone and the first column leach tests on the weathered Kary Zone ores are also planned to get underway next month.