Nordic Resources has recorded gold recoveries of up to 90% and copper recoveries of up to 91% at its Kopsa gold-copper project in Finland using a conventional processing route. The results will feed into an updated resource estimate expected in October, while a new 12,000-metre drilling program is already under way.
- Up to 90% gold and 91% copper recovery
- High-grade copper concentrates carrying payable gold and silver
- Consistent results across stockwork and tonalite samples
- Potential for improved recoveries from finer grinding
- Updated Kopsa resource estimate due next month
Kopsa testing delivers strong recovery across ore types
Nordic Resources Ltd (ASX:NNL) has cleared an important technical hurdle at its Kopsa gold-copper project, with locked-cycle testing producing 90% gold recovery and 91% copper recovery from the higher-grade stockwork material. The lower-grade tonalite material also performed strongly, returning 86% gold and 88% copper recovery under the same broad processing approach.
The results came from testing 11 samples representing the two main mineralisation styles at Kopsa. Variability testing produced average gold recoveries of 90% for stockwork and 88% for tonalite, with the company reporting little variation across the tested head grades. Silver recovery ranged from 76% to 82% in the locked-cycle tests.
Conventional flowsheet produces valuable concentrates
Blue Coast Research used a conventional circuit involving grinding to 80% passing 70 microns, copper flotation, bulk sulphide flotation and leaching. The gold was described as consistently free milling, meaning the tested route did not require sulphide pre-oxidation to achieve the reported recoveries.
The initial copper flotation stage produced concentrates containing 24% copper, 115 grams per tonne gold and 301 grams per tonne silver from the stockwork composite. The tonalite concentrate contained 25% copper, 42 grams per tonne gold and 260 grams per tonne silver. The company says deleterious elements were below smelter rejection limits, although arsenic averaged less than 1% in the stockwork concentrate and about 2% in the tonalite concentrate, potentially attracting modest penalty charges.
Metallurgy now feeds resource and drilling milestones
The work completes Kopsa's initial metallurgical program and is intended to provide inputs for the updated mineral resource estimate, which Nordic expects to release in October. Kopsa currently contains 23.2 million tonnes at 1.09 grams per tonne gold equivalent for 814,800 ounces, although that equivalent calculation still uses an older formula based on historical commodity prices and recovery assumptions. Nordic says the formula will be updated using the latest metallurgical results and commodity price forecasts.
The company has also started a new 12,000-metre drilling program at Kopsa. The next metallurgical phase is expected to operate at pre-feasibility-study level, with more samples selected using geological, spatial, mining-sequence and grade factors. It will also assess mineralogy, tailings behaviour, leach chemistry and the economic effect of grinding more finely.
Strong laboratory results still leave project economics open
Comminution testing found the ore reasonably hard and abrasive but amenable to semi-autogenous milling, with an average Bond work index of 17.8 kilowatt-hours per tonne. Nordic points to Finland's relatively low-cost power environment as providing flexibility to test finer grind sizes, after historical work indicated that gold recovery improved as the grind became finer.
For now, the results establish a promising processing response rather than a mine plan or project return. The small initial sample set, possible arsenic penalties, future grind-size costs and the need for broader geometallurgical testing all remain relevant to the next assessment. Managing Director Robert Wrixon said the company would incorporate the results into the October resource update, making that estimate the next test of whether the encouraging metallurgy translates into a larger and more credible Kopsa opportunity.
Bottom Line?
The metallurgy strengthens Kopsa's technical case, but the October resource update and later PFS work must show whether recovery quality can support economic development.
Questions in the middle?
- How much will the updated Kopsa resource grow after incorporating 9,631 metres of recent drilling?
- Will finer grinding improve recoveries enough to justify its additional power and operating costs?
- What concentrate payability and arsenic penalties will emerge from larger-scale testing?