Three drill rigs are turning on site, with two of these testing the high-grade Northeast zone target discovered last summer. The program is part of a broader effort to revive the Mount Polley mine, which produced more than 60,000 tonnes copper and 370,000 oz. gold from 1997 through 2001.
The Northeast zone has returned grades well above those of existing reserves, which stood at 31.9 million tonnes grading 0.36% copper and 0.34 gram gold when operations were suspended in 2001, owing to low metal prices.
The updated reserve/resource estimate being prepared will include data from all drilling completed to date at the Northeast, Bell and Springer zones.
At the Bell zone, recent definition and depth extension drilling returned a high of 0.5% copper and 0.43 gram gold over 219 metres. Ongoing drilling at the Springer Zone is continuing to intersect wide mineralized intervals beneath the design limits of the unmined Springer pit.
Imperial is testing the leaching of copper oxide ores, which typically had low recoveries in the past because the mill was designed to produce concentrates from sulphide deposits. Most of the remaining reserves in the yet-unmined Springer pit come from copper-oxide minerals.
Preliminary tests on the oxidized material have shown that about 80% of the acid-soluble copper can be recovered, compared with recoveries of 11% when oxide ores were treated in the existing flotation plant. If ongoing results confirm these recoveries, Imperial would forge ahead with plans to permit and develop a leaching plant that would operate alongside the existing flotation plant, thereby boosting overall recoveries.
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