Coda Minerals Strengthens Elizabeth Creek Leach Case With High Copper and Silver Recoveries
Coda Minerals has reported average copper and silver extraction of 94.4% and 95.9% respectively from representative Emmie Bluff samples, strengthening the case for its preferred whole-ore chloride leach process. The preliminary laboratory results also suggest Elizabeth Creek site water is suitable for processing, although cobalt recovery, plant-scale performance and capital requirements remain unresolved.
- 94.4% average copper extraction across representative Emmie Bluff composites
- 95.9% average silver extraction, with peak results of 99.7%
- Elizabeth Creek site water improved final copper, silver and cobalt extraction versus tap water
- Cobalt extraction averaged 39.7% and reached 51.7% in one sample
- Further variability testing and flowsheet selection remain ahead of the PFS
Copper and Silver Recoveries Hold Across Variable Samples
Coda Minerals Limited (ASX:COD) has produced some of its strongest metallurgical evidence yet for the preferred processing route at its Elizabeth Creek Copper-Silver Project, with representative Emmie Bluff samples averaging 94.4% copper extraction and 95.9% silver extraction after 24 hours of whole-ore chloride leaching. Peak results reached 97.2% for copper and 99.7% for silver.
The results came from four samples the company considers representative of expected Emmie Bluff production. Across that group, copper extraction ranged from 87.0% to 97.2%, while silver extraction ranged from 90.8% to 99.7%. A deliberately low-grade, chalcopyrite-rich sample still produced 90.0% copper and 86.8% silver extraction, although Coda excluded it from the representative averages.
One Windabout sample also returned 93.4% copper and 96.8% silver extraction after 24 hours. That result is encouraging for the broader processing pathway, but the company has not presented it as conclusive evidence that the same recovery profile will apply across the entire Elizabeth Creek project.
Site Water Performs Comparably to Perth Tap Water
A separate comparison tested the same Emmie Bluff composite using Elizabeth Creek site water and Perth tap water. After the final wash step used to recover precipitated metal solids, site water delivered 95.8% copper extraction and 93.6% silver extraction, compared with 95.1% and 92.9% respectively using tap water.
The difference was more pronounced for cobalt: site water produced 30.6% extraction against 24.0% with tap water. Coda said the result may reflect the higher natural salinity of the project water, although further testing would be needed to establish the cause. The practical conclusion is narrower but useful: the available site water did not appear to damage leaching performance under the laboratory conditions tested.
Cobalt Adds Potential Value but Remains a Processing Challenge
Cobalt extraction averaged 39.7% across the four representative Emmie Bluff composites and reached 51.7% in one sample. Coda’s existing whole-ore chloride leach economics exclude cobalt revenue, so any repeatable recovery could provide upside to future modelling. It is not yet an economic contribution: the company still needs to improve consistency, test recovery from leach residues and identify saleable downstream products.
The main technical difficulty is carrollite, the principal cobalt-bearing mineral at Elizabeth Creek. Coda says the mineral can resist oxidative leaching and may passivate during processing, while dissolved cobalt can be difficult to keep in solution. The company is testing chemistry changes, magnetic separation and low-cost flotation as possible ways to improve net cobalt recovery.
PFS Moves From Laboratory Results to Plant Design
The test work supports whole-ore chloride leach as the current PFS base case, but it does not settle the final flowsheet. Coda is still comparing that process with a flotation-based alternative incorporating an Albion hydrometallurgical circuit. Formal variability testing is planned after larger samples are generated through comminution work, with further testing also required at Windabout and MG14.
There is a cost consideration hiding beneath the attractive recovery figures. Coda says the final leach duration may be longer than assumed in the earlier Scoping Study, which could require more tankage and increase capital expenditure. The company expects any impact to depend on the final balance between leach time, solids ratio, recovery performance and plant design, but has not quantified it.
Ausenco has been appointed as principal process engineering consultant and is now undertaking metallurgical modelling, including work on reagent recycling and operating costs. Supporting PFS work continues across comminution, waste-rock characterisation, flood modelling, groundwater, tailings, environmental studies and mine planning. The next meaningful test is whether these laboratory recoveries survive translation into a complete, costed flowsheet.
Bottom Line?
The metallurgy is increasingly supportive, but the investment case still depends on converting high laboratory recoveries into a plant design with acceptable tankage, operating costs and cobalt recovery.
Questions in the middle?
- Will formal variability testing reproduce the copper and silver recoveries across Windabout, MG14 and additional Emmie Bluff material?
- How much additional capital will be required if the final process needs longer leach residence times and larger tanks?
- Can Coda establish a consistent, economic pathway to recover cobalt and include it in future project economics?
