Montreal-based Osisko Metals reports successful results for pre-concentrating test work using material sorters. Two technologies were tested - x-ray transmission sorting and dense media separation.
Representative samples were prepared of material from Osisko's Pine Point zinc-lead project 65 km east of Hay River. Pre-concentration of the ore can significantly reduce the cost of haulage and milling.
The x-ray transmission (XRT) sorting returned these results:
Zinc recoveries ranged from 76.5% to 98.0% (average of 92.6%);Lead recoveries ranged from 94.9% to 99.7% (average of 97.8%);Mass pull ranged from 34.4% to 73.5% (average of 49.1%); andAverage grade of rejected material is 75% zinc and 0.047% lead.Dense media separation (DMS) provided these results:
Zinc recoveries ranged from 76.7% to 96.2% (average of 92.4%);Lead recoveries ranged from 87.4% to 98.7% (average of 95.3%);Mass pull ranged from 12.8% to 61.5% (average of 30.4%); andAverage grade of rejected material is 75% zinc and 0.08% lead.Osisko said that the results were similar, but it will probably near-pit use XRT methods. XRT works with dry samples that are easy to handle when the weather gets cold. The XRT equipment is also more mobile than DMS equipment. That would be a major benefit as mining could move from one deposit to another on the property.
Pine Point was last mined by Cominco from 1975 to 1988. The weighted average zinc recovery of 91.91% for a head grade of 6.54% zinc, producing a concentrate grade of 58% zinc. The lead recovery averaged 88.69% for a head grade of 2.56% lead, producing a concentrate grading 75.68% lead. Osisko expects that its flotation tests of pre-concentrated ore to the historic records will at least match the historic results.
The Pine Point project currently has an inferred mineral resource of 39.4 million tonnes grading 4.58% zinc (containing 3.9 billion lb. of zinc) and 1.85% lead (containing 1.6 billion lb. of lead).
(This article first appeared in the Canadian Mining Journal)