Perth – October 14, 2026 -- Sun Silver Limited (ASX: SS1; OTCQX: SSLVF) recovered 84.5% of silver and 83.6% of gold within 24 hours in cyanide leach testwork on its Maverick Silver Project in Nevada, strengthening the case for a tank-leach/CIL processing route alongside heap leach.
Sample 1 test delivers peak recoveries within 48 hours
The top result came from Sample 1 (LT15), run at a P80 53μm grind with 5,000 ppm initial and 2,500 ppm maintained sodium cyanide and no lead nitrate. Head assay recoveries were 84.5% for silver and 83.6% for gold, with peak recoveries indicated between 0 and 48 hours. Most recoverable metal in the test was extracted in the first 24 hours.
Interim solution assays for Sample 1 pointed to higher extraction at 24 and 48 hours than the reported figures, which are calculated from final head assay grades. The company notes that interim extractions are indicative point-in-time calculations, not final recoveries.
Lower-reagent test on Sample 2 recovers about 87.6% of silver
An optimisation test on Sample 2 (LT22) used 3,000 ppm initial and 1,500 ppm maintained cyanide, with 500 ppm lead nitrate and the same grind. It returned silver recovery of about 87.6% to 87.7% (the source gives both figures) and gold recovery of 87.5%, with peak recoveries between 0 and 48 hours.
The ongoing program will test whether a balanced cyanide and lead nitrate regime can match the high-cyanide results while cutting reagent consumption and operating costs.
Lead nitrate speeds early silver extraction but fades at high cyanide
Under standard cyanide conditions, lead nitrate accelerated silver extraction in both samples. At elevated cyanide concentrations its incremental benefit fell materially by 48 hours. In Sample 1, 48-hour silver recoveries were similar with and without lead nitrate, so its main effect was faster early extraction.
Silver extraction also accelerated under elevated cyanide. The company says silver cyanidation can need more intensive conditions than free-milling gold, and is sensitive to free cyanide, dissolved oxygen, mineralogy and residence time.
IMO tests 242 core intervals across two composites
Independent Metallurgical Operations (IMO), a subsidiary of SGS, designed, ran and reviewed the work. Testing used 242 intervals of half diamond drill core of oxide and transitional mineralisation, split into Composite 1 (147kg) and Composite 2 (127kg). IMO ran five bottle-roll tests on Sample 1 and six on Sample 2 in deionised water, avoiding chloride variations in Perth tap water.
The program builds on earlier bottle-roll and cyanide leach results that gave initial heap-leach and tank-leach recovery estimates and showed no evidence of preg-robbing.
Tank-leach/CIL route could widen options for antimony recovery
Sun Silver is evaluating heap-leach and higher-recovery tank-leach/CIL pathways in parallel. It says a tank-leach/CIL flowsheet may offer more flexibility for antimony recovery, and it is working toward a maiden antimony Mineral Resource Estimate.
The company continues to engage the U.S. Government, including the Department of Commerce and the Permitting Council, on Maverick's potential role in domestic silver and critical-mineral supply chains. That includes possible pathways for government support.
Managing Director Andrew Dornan said the results show "rapid silver and gold extraction within just 24 hours" and clear room to optimise recoveries and reagent use. The next phase of work targets higher recoveries with lower reagent consumption, grind requirements and processing costs.