- 01Silver recovery reached 87.7%; gold, 87.5%.
- 02Most metal extracted within 24 hours.
- 03Sun Silver is assessing tank leach vs heap leach and process settings.
Sun Silver (ASX: SS1) has recorded rapid silver and gold extraction in fresh metallurgical testing at its Maverick silver project in Nevada, strengthening the case for evaluating a conventional tank-leach processing route.
The latest cyanide leach trials returned final recoveries of 84.5% silver and 83.6% gold from one composite sample, with most recoverable metal extracted within the first 24 hours.
A second composite achieved final recoveries of 87.7% silver and 87.5% gold under a lower-cyanide reagent regime, giving the explorer another option for refining processing conditions.
The work forms part of a broader program comparing tank leaching with heap leaching as Sun Silver considers recovery rates, reagent requirements, and potential antimony production.
Sun Silver will now examine how cyanide and lead nitrate consumption, particle size, and leach residence time interact before selecting preferred process settings.
Rapid Extraction Studies
Independent Metallurgical Operations conducted 11 cyanide bottle-roll tests using two composite samples drawn from 242 intervals of existing diamond drill core containing oxide and transitional mineralisation.
The composites weighed 147 kilograms and 127kg, with testing examining cyanide concentration, lead nitrate, dissolved oxygen, and grind size to assess their effects on extraction speed.
The stronger-reagent test on the first sample produced rapid extraction without lead nitrate, while the second sample demonstrated comparable final performance with a lower cyanide dose and lead nitrate addition.
Although interim solution assays showed higher indicative extraction percentages in some tests, Sun Silver distinguished those point-in-time calculations from the final recoveries established using head assays.
The rapid leach response provides data for assessing processing residence times, plant configuration and the economics of a possible tank-leach and carbon-in-leach (CIL) flowsheet.
Further Opportunities Identified
Comparative trials showed lead nitrate could accelerate early silver extraction under standard cyanide conditions, although its additional benefit diminished after 48 hours at higher cyanide concentrations.
On the second composite, a reduced-reagent trial extracted 85.3% of silver after 24 hours and 85.4% after 48 hours, compared with 86.6% and 87.1% under a higher-cyanide regime without lead nitrate.
Another test using a coarser grind achieved 83.9% silver extraction after 24 hours and 83.7% after 48 hours, suggesting scope to investigate reduced grinding energy requirements.
“The results highlight clear opportunities to further optimise recoveries, reagent consumption and processing conditions as we evaluate the optimal development pathway,” managing director Andrew Dornan said.
“With active US government engagement focused on large-scale domestic development, maximising US metal production, and strengthening critical mineral supply chains, we continue to evaluate processing options capable of maximising silver, gold, and potential antimony recovery.”
Antimony Recovery Potential
The company is assessing both heap-leach and tank-leach / CIL alternatives, with the latter potentially providing more flexibility to recover antimony alongside silver and gold.
Sun Silver is working towards a maiden antimony mineral resource estimate and remains engaged with United States government agencies, including the Department of Commerce and Permitting Council, over potential domestic metals production and project support.
Maverick has an existing inferred mineral resource of 237.3 million tonnes grading 45.5 grams per tonne silver and 0.30g/t gold, containing 347.2 million ounces silver and 2.25Moz gold.
The resource also contains 539Moz of silver equivalent, although the deposit remains open along strike and at depth and development decisions require further technical and economic evaluation.
Additional intermittent bottle-roll, column-leach, and cyanide leach tests across representative mineralisation will assess variability and help determine the preferred processing pathway for Maverick.
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