Computer analysis reveals new reserves at Cochenour

Operated by Inco Gold, a wholly- owned affiliate of Inco Ltd., the program is designed to test four areas of potential gold mineralization.

These targets were identified by Inco geologists following a thorough review of all the mine’s historical production and drill data. This information was correlated on a computer which led to the identification of potential reserve blocks. Inco estimates the four zones host potential reserves of 1.3 million tons grading 0.25 oz gold per ton.

During its operating life, the Cochenour Willans mine produced 1.2 million oz of gold from 2.3 million tons of ore. The mine shut down in 1971 following 32 years of production.

The main shaft has been dewatered to the 2,200-ft level. It extends to a depth of 2,600 ft. To the end of September, Inco plans to have completed more than 60,000 ft of diamond drilling and detailed sampling of several levels throughout the mine. “Structurally the mine is in good shape,” Terrence Podolsky, president of Wilanour and vice- president exploration at Inco Ltd., told The Northern Miner. “Our underground sampling is confirming the old mine records.”

What has the project partners excited is the potential for finding additional ore in zones previously rejected as economic ore hosts by the mine’s former operators.

A priority target are the chert horizons within the Rhyolite X zone. Inco estimates that between the 1,425-ft and 2,600-ft levels, these chert units host about 625,000 tons grading 0.21 oz gold, based on Cochenour drill data. However, a study comparing drill-indicated grades with mill head grades shows a pronounced nugget effect.

“The drill-indicated grade (across the width of the chert) is consistently a bout a quarter of the mill head grade. This was one of the reasons why Cochenour ignored this rock type as a potential ore host,” an internal Inco report concludes. “For the stopes examined here or mined for smelter flux, the mill head grade was 0.232 whereas the drill-indicated grade was 0.047, or 20%,” the Inco report says.

Surface exploration is examining the up-dip extension of these chert zones. The partners will be trying to correlate several surface showings with known chert horizons identified from underground.

A 400-ton-per-day mill was upgraded in 1981 and mothballed the following year. Additional refurbishing would be required to make the mill operational.

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