Sun Silver Reports 87% Silver and Gold Recovery in Maverick Cyanide Testwork
Key Takeaways
- Sample 2 (LT22) delivered 87.7% silver and 87.5% gold recovery on a head assay basis, while Sample 1 (LT15) returned 84.5% silver and 83.6% gold, with most metal extracted within 24 hours.
- LT22 achieved its result on 3,000 ppm initial cyanide against 5,000 ppm for the higher-dose tests, pointing to possible operating cost savings that still need confirming.
- A coarser P80 106μm grind (LT23) still returned 83.9% silver at 24 hours, and the next testwork phase will evaluate coarser grinds.
- The Maverick JORC Inferred resource stands at 237Mt for 347.2Moz silver and 2.25Moz gold (539Moz silver equivalent), but Inferred is the lowest confidence category.
- Sun Silver is assessing tank-leach/CIL alongside heap-leach, is engaging U.S. Government bodies with no support secured, and has given no dates for optimisation results or a maiden antimony resource.
Rapid silver and gold recoveries confirmed at Maverick
Sun Silver (ASX: SS1; OTCQX: SSLVF) reported optimised cyanide leach testwork at the Maverick Silver Project in Nevada, showing rapid silver recovery and gold extraction within 24 to 48 hours. For investors weighing how the project might eventually be processed, that speed matters.
Sample 1 (LT15) delivered 84.5% silver and 83.6% gold recovery on a head assay basis. Sample 2 (LT22) delivered 87.7% silver and 87.5% gold on a head assay basis, using a lower reagent dosage.
The work was designed, undertaken, managed and reviewed by Independent Metallurgical Operations (IMO), a subsidiary of SGS. Two composite samples (147kg and 127kg total weight) were built from 242 intervals of half diamond drill core, comprising oxide and transitional mineralisation.
The company said the speed of extraction is particularly encouraging for its assessment of a conventional tank-leach/CIL flowsheet, where recovery, leach kinetics and residence time feed into process design and economic evaluation.
Andrew Dornan, Managing Director, Sun Silver
“These results continue to demonstrate the strong metallurgical characteristics of Maverick, with rapid silver and gold extraction within just 24 hours providing further confidence in the Project’s development potential…”
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Testwork results: what the numbers show
Five cyanide leach bottle-roll tests were run on Sample 1 and six on Sample 2. They varied reagent regimes and grind sizes to see how each affected extraction.
Standout Sample 1 result (LT15)
LT15 was the standout. It used a P80 53μm grind (P80 means 80% of the material is ground finer than that size), 5,000 ppm initial and 2,500 ppm-maintained sodium cyanide (NaCN), and no lead nitrate.
Head assay results showed 84.5% silver and 83.6% gold recovery, with peak recoveries indicated between 0 and 48 hours. The company said the majority of recoverable silver and gold in this test was extracted within the first 24 hours.
Strong recoveries at reduced cyanide (LT22)
LT22 on Sample 2 used a more moderate regime: P80 53μm, 3,000 ppm initial and 1,500 ppm-maintained NaCN, and 500 ppm lead nitrate. Head assay results were 87.7% silver and 87.5% gold.
Lower reagent use could point to lower operating costs, though the company says further testwork is needed to confirm whether a balanced combination can match the higher cyanide regime.
The table below shows interim figures at set time points. These differ from the final head assay headline numbers.
| Test | Sample | Grind P80 | NaCN initial/maintained | Silver recovery (24hr / 48hr) |
|---|---|---|---|---|
| LT15 | Sample 1 | 53μm | 5,000 / 2,500 ppm | 88.6% / 91.9% |
| LT22 | Sample 2 | 53μm | 3,000 / 1,500 ppm | 85.3% / 85.4% |
| LT20 | Sample 2 | 53μm | 5,000 / 2,500 ppm | 86.6% / 87.0% |
| LT23 | Sample 2 | 106μm | 5,000 / 2,500 ppm | 83.9% / 83.7% |
The company flagged possible upside: Sample 1 interim solution assays indicate higher extraction percentages than the reported recoveries, which are calculated using final head assay grades.
Interim 24 and 48 hour percentages are indicative point-in-time calculated extractions, not final or ultimate recoveries. Treat them as snapshots of performance, not end results.
Tank-leach/CIL pathway and reagent optimisation
What is tank-leach/CIL and why recovery speed matters
Heap leach stacks crushed ore in piles and trickles solution through it. Tank leach grinds the ore finer and mixes it with solution in tanks, and carbon-in-leach (CIL) adds carbon to capture dissolved metal as it leaches.
In tank processing, faster leaching can mean shorter residence time (how long material stays in the tanks), which feeds into plant configuration and economics. Reagent use and grind size also affect costs.
Sun Silver is assessing a conventional tank-leach/CIL pathway alongside heap-leach scenarios. The company said all development options remain open.
Lead nitrate and cyanide findings
Lead nitrate accelerated silver extraction in both samples under standard cyanide conditions. At elevated cyanide concentrations, its incremental benefit reduced materially by 48 hours.
In Sample 1, lead nitrate accelerated early silver extraction, while 48-hour silver recoveries were similar between the tests. Silver extraction also accelerated under elevated cyanide, so the aim is the optimal balance between recovery and reagent consumption.
The next phase of optimisation will focus on:
- Optimising cyanide and lead nitrate dosage
- Evaluating coarser grind sizes, with LT23 at P80 106μm achieving 83.9% silver at 24 hours and 83.7% at 48 hours
- Expanding variability testwork across additional representative Maverick mineralisation
- Advancing tank-leach/CIL flowsheet development
Strategic context: U.S. engagement and antimony optionality
Sun Silver continues active engagement with various U.S. Government bodies, including the Department of Commerce and Permitting Council. The discussions concern Maverick’s potential role in strengthening domestic silver and critical-mineral supply chains, including potential pathways for U.S. Government support. No support has been announced as secured.
The company also said a tank-leach/CIL flowsheet may provide greater flexibility for potential future antimony recovery. It is working towards a maiden antimony Mineral Resource Estimate, though the announcement gives no timing.
The project sits in Nevada, which the Fraser Institute rated the Number 1 mining jurisdiction in the world in 2025. For you as an investor, that pairs a jurisdiction angle with a critical minerals theme, though both remain early-stage at Maverick.
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Maverick’s scale and what comes next
Maverick is located 85km from the town of Elko and is proximal to the Carlin Trend, surrounded by operations including Barrick’s Carlin Mine. Key resource details:
- JORC Inferred Mineral Resource of 237Mt grading 45.5g/t silver and 0.30g/t gold
- 347.2Moz of contained silver and 2.25Moz of contained gold (539Moz contained silver equivalent)
- Deposit remains open along strike and at depth
An Inferred resource carries the lowest geological confidence category under the JORC Code, so the numbers can change as work continues.
A parallel metallurgical program is running across additional representative material from the Mineral Resource. It includes Intermittent Bottle Roll, column-leach and cyanide bottle-roll testwork, and is designed to optimise the balance between metal recovery, capital and operating costs.
Pending catalysts are further optimisation results and the expanded variability testwork. The announcement does not give dates for either.
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