Vancouver —
The large-core holes (4- and 3.3-inch diameter) were drilled early this year to collect material for metallurgical testing, and have recovered about 38 tonnes of rock.
From a total of almost 2,700 samples, about 2,100 intervals were used to provide three composites sent for assay. From over 1,900 metres of core tested, an average grade of about 0.42% copper, 0.12% nickel, 0.5 gram platinum-palladium-gold per tonne and 0.009% cobalt was returned, correlating well with previous results.
Holes were drilled from 11 sites, spread across the strike of the deposit, targeting an envelope representing the initial 10 years of planned mining at NorthMet.
Samples were also sent to SGS Lakefield Research Laboratories for pilot-scale metallurgical testing.
The company recently reviewed an updated mining plan for NorthMet citing lower costs than previously estimated. The study modelled a 25,000-tonne-per-day operation with mining costs of around US$1 per tonne and a processing cost of US$6 per tonne.
Indicated resources (above the 152-metre elevation and using a 0.2% copper cutoff) are 215 million tonnes grading 0.31% copper, 0.09% nickel and 0.007% cobalt, with 0.3 gram palladium, 0.08 gram platinum and 0.04 gram gold per tonne. Additional inferred resources of 110 million tonnes grading 0.32% copper, 0.08% nickel, 0.006% cobalt, 0.3 gram palladium, 0.1 gram platinum and 0.05 gram gold were also calculated.
Redesign of the pit has also improved potential operating economics, significantly dropping the planned stripping ratio from 4.3 to 1.1. PolyMet plans to float a sulphide concentrate, then pressure-oxidize it using its PlatSol technology and produce cathode copper by solvent extraction-electrowinning. The plant would also produce byproduct nickel and cobalt hydroxides and a precious metal-bearing sludge.
The NorthMet deposit occurs in the Duluth intrusive complex, a large composite layered tholeiitic mafic intrusion along a Middle Proterozoic mid-continental rift. Along with several other copper-nickel deposits, NorthMet is along the western edge of the complex, in troctolitic and minor gabbroic intrusions. The area also hosts a number of large taconite iron-ore deposits currently being mined.
With 67 million shares outstanding, PolyMet had $67-million market capitalization at its recent trading level of $1 per share.
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