Metallurgical tests on material pulled from the NorthMet copper-nickel project in northern Minnesota are returning encouraging results for
The bio-leach testing is being carried out by Australia’s BacTech Metallurgical Solutions.
In April, PolyMet released preliminary results from pressure oxidation tests performed by Lakefield Research. The bio-leach tests have returned comparable results for copper and nickel, though the recoveries were somewhat lower for platinum, palladium and gold. Pressure oxidation recovered 94% of the metals, whereas bio-leaching recovered 89% of the gold and 78% of the palladium. The platinum recovery has yet to be completed, though the company expects it will be lower than that achieved by pressure oxidation. However, bio-leaching is much less costly than pressure oxidation.
Silver extraction from the leaching was 38%, considerably higher than with the pressure method.
PolyMet will either choose one method over the other, or possibly meld the two into one hybrid process. A decision is expected in July.
The NorthMet deposit, formerly known as the Dunka Road project, is in the Duluth complex, a large layered mafic intrusion in the northwestern part of the state. The deposit has a strike length of 3 miles and has been tested to a depth of 2,400 ft. below the surface. Mineralization remains open at depth.
A 1991 resource estimate pegged the deposit at 808 million tonnes of sulphide mineralization grading 0.43% copper and 0.11% nickel, plus 1.5 grams silver, 0.06 gram gold, 0.44 gram palladium and 0.12 gram platinum.
The total mineral inventory stands at 1.45 billion tonnes averaging 0.4% copper, 0.09% nickel, 1.3 grams silver, 0.06 gram gold, 0.44 gram palladium and 0.12 gram platinum.
PolyMet has retained Union Securities to complete a brokered private placement for $5 million in special warrants. Each warrant, priced at $2, entitles the holder to buy one share and half a share purchase warrant. One share purchase warrant entitles the holder to buy a share for $2.50 each in the first year, or $3 in the second.
After the financing, PolyMet will have 23.6 million shares outstanding.
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