Aurora Tank Gold: Exceptional Heap Leach Recoveries Signal Low-Cost Production Pathway
Marmota Limited (ASX: MEU) has announced outstanding metallurgical results from its Aurora Tank gold project, achieving gold recoveries up to 93% through column leach testing—a remarkable figure that significantly strengthens the project’s commercial potential.
Breakthrough Metallurgical Results Point to Cost-Effective Development
The recent testing program was designed to evaluate Aurora Tank’s suitability for heap leach processing—a significantly less capital-intensive gold recovery method compared to traditional milling operations.
The results exceeded expectations, with:
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- 93% gold extraction from moderately weathered ore at 8mm crush size
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- 89% average recovery across five different sample composites
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- Rapid leaching kinetics with over 55% gold extraction within just 10 days
These exceptional recovery rates are particularly significant because heap leaching typically yields lower recoveries than conventional milling but at dramatically reduced capital and operating costs.
“Aurora Tank features multiple bonanza grades, predominantly close to surface, with soft ground, and now confirmed outstanding metallurgy amenable to low-cost low capex heap leach recovery,” stated Marmota Chairman Dr Colin Rose.
Testing Program Details
The comprehensive testing program was conducted by Australian Minmet Metallurgical Laboratories (AMML) and managed by heap leaching specialists Kappes Cassiday & Associates. The work involved:
| Composite Type | Weathering Style | Crush Size | Gold Extraction |
|---|---|---|---|
| Master Composite 1 | Moderately weathered | 8.0 mm | 93% |
| Master Composite 1 | Moderately weathered | 12.5 mm | 89% |
| Master Composite 2 | Partially weathered | 8.0 mm | 86% |
| Master Composite 2 | Partially weathered | 12.5 mm | 83% |
| Intermediate Composite 1 | Strongly weathered | 12.5 mm | 79% |
The testing program utilised 31 drill core subcomposites representing 197 metres of drill core, providing a robust dataset for evaluation.
Understanding Heap Leaching: A Cost-Efficient Gold Recovery Method
Heap leaching is a processing technique that involves stacking crushed ore on impermeable pads and applying a chemical solution (typically cyanide) that dissolves the gold. The gold-bearing solution is then collected and processed to recover the precious metal.
The key advantages over conventional milling include:
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- Substantially lower capital costs to build
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- No expensive mill or tailings dam required
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- Simpler operation with fewer moving parts
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- Lower operational costs per ounce of gold produced
The trade-off is typically lower metal recovery rates—which makes Aurora Tank’s exceptional 93% recovery figure particularly noteworthy, as it approaches levels typically associated with much more expensive conventional milling operations.
The testing program confirmed these metallurgical advantages at the Aurora Tank gold project, with results indicating the viability of a low-capital development pathway.
Aurora Tank: A High-Grade Gold Discovery
Aurora Tank has previously reported numerous high-grade gold intersections, including:
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- 112 g/t gold over 2m (including 1m @ 217 g/t)
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- 72 g/t gold over 3m (including 1m @ 197 g/t)
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- 67 g/t gold over 2m (including 1m @ 93 g/t)
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- 41 g/t gold over 3m (including 1m @ 120 g/t)
Many of these bonanza-grade intersections occur relatively close to surface, enhancing the project’s economic potential.
The combination of high grades and now confirmed excellent metallurgical performance positions the Aurora Tank gold project by Marmota Ltd as a particularly attractive development opportunity in the current gold price environment.
Strategic Importance Within Marmota’s Gold Portfolio
Aurora Tank serves as the flagship project in Marmota’s extensive gold portfolio within the Gawler Craton. The company owns all the gold deposits within a 10,000 km² area, including:
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- Aurora Tank
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- Campfire Bore (recently yielded bonanza grades over 100 g/t Au)
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- Golf Bore
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- Greenewood
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- Mainwood
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- Typhoon
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- Monsoon
This commanding land position gives Marmota significant strategic regional position in a period of record gold prices.
Technical Considerations for Heap Leach Development
The detailed test program provided several important technical insights for potential development planning:
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- Crush size flexibility: The high recoveries at both 8mm and 12.5mm crush sizes provide operational flexibility
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- Rapid leaching kinetics: Over 55% gold extraction within just 10 days indicates potential for efficient processing cycles
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- Low reagent consumption: Moderate cyanide consumption suggests field consumption for a short leach cycle would likely be in the 0.4 to 0.6 kg/t range
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- Minimal impurities: Low copper, silver, and mercury levels in the samples further enhance processing efficiency
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- Favourable physical characteristics: The weathered materials appear very friable with significant fines content, suggesting easy crushing with low abrasion
These factors potentially contribute to a straightforward processing configuration for the Aurora Tank gold project by Marmota Ltd, enhancing the economic case for development.
Why Investors Should Take Notice
Aurora Tank presents a compelling investment case based on several key factors:
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- Exceptional Metallurgy: The 93% recovery rate through heap leaching is extraordinary and significantly enhances project economics
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- Lower Development Costs: The confirmation of heap leach viability offers a potential low-capital pathway to production
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- High-Grade Resource: The presence of multiple bonanza-grade gold intersections close to surface enhances potential project economics
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- Strategic Regional Position: Marmota’s control of multiple gold deposits within a 10,000 km² area creates significant strategic value
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- Positive Gold Price Environment: With gold prices at record highs, the timing for advancing such projects is optimal
The Aurora Tank gold project by Marmota Ltd now appears positioned to rapidly advance as it ticks another crucial technical box on the path to potential development, bolstered by these exceptional metallurgical results that confirm the viability of a low-cost development pathway.
Future Development Pathway
Following these positive metallurgical results, Marmota is expected to incorporate the findings into its development planning. The confirmation of heap leach viability potentially simplifies the path to production by eliminating the need for complex milling facilities and tailings dams.
Furthermore, the rapid leaching kinetics observed in testing suggest the possibility of efficient processing cycles, which could enhance cash flow profiles during potential future operations.
Marmota has indicated it intends to review the results and consider trials extended to fresh rock with High Pressure Grinding Roll (HPGR) crushing, which could further optimise processing parameters as the project advances.
The combination of these factors points to an encouraging development outlook for Aurora Tank, with the metallurgical results addressing one of the key technical considerations for any potential mining operation.
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