Rapid Silver and Gold Recoveries From Metallurgical Test Work

Highlights:

• Impressive silver and gold recoveries achieved from the latest round of optimised cyanide leach testwork at the Maverick Silver Project, demonstrating rapid silver and gold extraction within 24 to 48 hours.
• The Company is undertaking a range of metallurgical testwork to optimise silver-gold extraction and provide optionality in processing pathways that will be considered in future studies.
• Sample 1 (LT15) achieved rapid silver and gold extraction within 24 hours under the same leach conditions (P80 53µm grind; 5,000 ppm initial / 2,500 ppm-maintained NaCN; no lead nitrate): 
  • Head assay results, 84.5% silver and 83.6% gold recovery with peak recoveries indicated between 0 and 48 hours.
• A lower-reagent optimisation test on Sample 2 (LT22) also delivered rapid silver extraction (P80 53µm grind; 3,000 ppm initial / 1,500 ppm-maintained NaCN; 500 ppm lead nitrate): 
  • Head assay results, 87.7% silver recovery and 87.5% gold recovery with peak recoveries indicated between 0 hours and 48 hours.
• Possible upside exists for silver and gold recoveries at 24 and 48 hours, with Sample 1 interim solution assays indicating higher extraction percentages than the reported recoveries calculated using final head assay grades.
• Silver extraction accelerated under elevated cyanide, with further optimisation targeting the optimal balance between recovery and reagent consumption.
• Tank-leach/CIL may provide greater flexibility for potential antimony recovery. The Company is in the process of working towards a maiden antimony Mineral Resource Estimate.
• Continued active U.S. Government (Department of Commerce) engagement, focused on large-scale domestic development and maximising U.S. production of silver and critical minerals including antimony and gold, further reinforces the strategic rationale for also evaluating higher recovery tank leach/CIL development pathways at Maverick.

PERTH, Australia, Oct. 14, 2026 /PRNewswire/ -- Sun Silver Limited (ASX: SS1; OTCQX: SSLVF) ("Sun Silver" or "the Company") is pleased to report highly encouraging results from its ongoing metallurgical activities for the Maverick Silver Project in Nevada, USA ("Maverick" or "the Project"). 

Sun Silver Managing Director, Andrew Dornan, said:

"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. The results highlight clear opportunities to further optimise recoveries, reagent consumption and processing conditions as we evaluate the optimal development pathway. With active U.S. Government engagement focused on large-scale domestic development, maximising U.S. metal production and strengthening critical mineral supply chains, we continue to evaluate processing options capable of maximising silver, gold and potential antimony recovery."

Metallurgical Testwork - Update

As part of the Company's larger ongoing metallurgical testwork program evaluating and optimising potential processing pathways for the Project, the work detailed within this announcement focused specifically on accelerating silver extraction within the first 48 hours through optimisation of cyanide concentration, lead nitrate addition, dissolved oxygen and grind size.

This series of testwork was devised to build on and complement the previous exceptional silver-gold recovery results from Intermittent Bottle Roll and Cyanide Leach testwork that provided an initial estimate of heap-leach and tank-leach recoveries, respectively, and showed no evidence of preg-robbing .

Metallurgical testwork was designed, undertaken, managed and reviewed by Independent Metallurgical Operations ("IMO"), a subsidiary of SGS. Samples utilised for this testwork were derived from the same composites of the initial testwork program1. The tests were conducted in deionised water, so it mitigates against known chloride ion concentration variations in Perth tap water.

A total of 242 intervals of half diamond drill core were derived from existing diamond core samples, comprising oxide and transitional mineralisation. Two composite samples were prepared:

• Composite sample 1: 147kg total weight
  
  
• Composite sample 2: 127kg total weight

Five cyanide leach bottle-roll tests were undertaken on Sample 1 and six tests on Sample 2, allowing the Company to assess the effect of varying reagent regimes and grind sizes on silver and gold extraction.

The standout result was achieved from Sample 1 (LT15), which demonstrated rapid extraction of both silver and gold under the LT15 leach conditions.

Head assay results, 84.5% silver and 83.6% gold recovery with peak recoveries indicated between 0 hours and 48 hours.

The rapid extraction of both silver and gold within the first 24 to 48 hours is particularly encouraging for the Company's assessment of a conventional tank-leach/CIL processing flowsheet, where recovery, leach kinetics and residence time are important inputs into process design and economic evaluation.

Strong Recoveries at Reduced Cyanide Dosage

Importantly, a subsequent optimisation test on Sample 2 (LT22) evaluated silver-gold recovery under a more moderate cyanide regime combined with a reduced lead nitrate dosage.

Head assay results, 87.6% silver recovery and 87.5% gold recovery 

The ongoing program will seek to determine whether a balanced combination of cyanide and lead nitrate can deliver comparable metallurgical performance to the higher cyanide regime while reducing overall reagent consumption and operating costs.

Lead Nitrate and Early-Stage Leach Kinetics

Comparative tests assessed the introduction of lead nitrate as a potential means of accelerating silver and gold leach kinetics.

Testwork shows that the addition of lead nitrate under standard cyanide conditions accelerated silver extraction in both samples, supporting further assessment of lead nitrate as part of reagent optimisation.

At elevated cyanide concentrations, the incremental benefit of lead nitrate reduced materially by 48 hours. In Sample 1, lead nitrate accelerated early silver extraction, while the 48-hour silver recoveries were similar between the tests, indicating that its principal benefit under the conditions tested was accelerated early-stage extraction.

Silver Leach and Reagent Optimisation

The Maverick testwork demonstrates the impact of cyanide concentration on the rate of silver extraction.

Silver cyanidation can require more intensive leach conditions than conventional free-milling gold cyanidation. Silver extraction can be sensitive to free cyanide concentration, dissolved oxygen, mineralogy and leach residence time, making optimisation of the overall reagent regime an important component of flowsheet development.

These results highlight an important optimisation opportunity for Maverick: determining the optimum balance between cyanide concentration, lead nitrate dosage, dissolved oxygen and residence time to maximise silver and gold recovery and leach kinetics while minimising reagent consumption and processing costs.

Tank Leach Provides Potential High-Recovery Development Pathway

The latest results provide further support for Sun Silver's assessment of a conventional tank-leach/CIL processing pathway, alongside heap-leach development scenarios currently being evaluated for Maverick.

The ability to achieve 84.5% silver and 83.6% gold recovery within only 24 hours (Sample 1 results) provides an important technical basis for evaluating a high-recovery processing configuration.

The Company considers the speed of extraction particularly encouraging. The majority of recoverable silver and gold in the standout test was extracted within the first 24 hours. This provides important information for ongoing optimisation of residence time, plant configuration and processing economics.

Recovery Disclosure: Silver and gold extraction percentages reported at interim time intervals (including 24 and 48 hours) represent indicative point-in-time calculated extractions, determined from solution assays collected at the relevant sampling time and the back-calculated head grade. Accordingly, interim extraction results are indicative of metallurgical performance at the stated point-in-time and should not be interpreted as final or ultimate recoveries.

U.S. Strategic Importance and Optionality for Antimony Recovery

Sun Silver continues active engagement with various U.S. Government including Department of Commerce and Permitting Council regarding Maverick's potential role in strengthening domestic silver and critical-mineral supply chains, including potential pathways for U.S. Government support for the Project.

These engagements reflect a strategic focus on large-scale domestic development and maximising the recovery and production of U.S. sourced metals. Together with Maverick's substantial silver-gold Mineral Resource and emerging antimony potential, this reinforces the importance of evaluating development scenarios capable of maximising metal recovery and production at scale.

Accordingly, the Company is continuing to evaluate both heap-leach and higher-recovery tank-leach/CIL processing pathways, including the potential for a tank-leach/CIL flowsheet to provide greater flexibility for potential future antimony recovery. All development options remain open, with metallurgical, technical and economic investigations continuing to determine the optimal development pathway for Maverick.

Next Phase of Tank-Leach / CIL Metallurgical Optimisation

The latest testwork has identified several clear opportunities to further optimise the Maverick processing flowsheet, with the next phase of metallurgical work focused on maximising recoveries while reducing reagent consumption, grind requirements and processing costs.

The optimisation program will focus on:

• Optimising cyanide and lead nitrate dosage: Results indicate that a lower-reagent regime may achieve silver recoveries approaching those achieved under the elevated cyanide conditions. Sample 2 (LT22) achieved 85.3% silver recovery within 24 hours and 85.4% within 48 hours (P80 53µm; 3,000/1,500 ppm NaCN; 500 ppm lead nitrate), compared with 86.6% and 87.0% respectively for LT20 (P80 53µm; 5,000/2,500 ppm NaCN; no lead nitrate). Further testwork will target the optimum balance between cyanide and lead nitrate dosage, recovery and reagent consumption. 
• Evaluating coarser grind sizes: Initial testing indicates the potential to maintain strong silver extraction at a substantially coarser grind. Sample 2 (LT23) at P80 106µm achieved 83.9% silver recovery within 24 hours and 83.7% within 48 hours (5,000/2,500 ppm NaCN; 1,000 ppm lead nitrate). Further work will assess whether high recoveries can be maintained at coarser grind sizes, potentially reducing grinding energy requirements and processing costs. 
• Expanding variability testwork: The Company intends to expand testing across additional representative Maverick mineralisation to assess metallurgical performance across different mineralogical domains, grades and styles of mineralisation. This work will seek to establish the consistency of silver and gold recoveries across the broader Mineral Resource.
• Advancing tank-leach/CIL flowsheet development: Further testwork will build on the encouraging bottle-roll results and evaluate the parameters required for a potential commercial tank-leach/CIL flowsheet, including residence time, grind size, reagent consumption and other key process-design parameters.

Further to the test work detailed in this announcement, the Company has a significant metallurgical testwork program running in parallel across additional representative material selected from throughout the Maverick Silver Mineral Resource. This program includes Intermittent Bottle Roll, column-leach and cyanide bottle-roll leach testwork under a range of operating conditions. The program is designed to optimise the balance between metal recovery, capital and operating costs, including assessment of grind size, associated power requirements, reagent consumption and leach performance, to support selection of the preferred processing pathway for Maverick.

SOURCE Sun Silver Ltd.