“Flotation testwork on leach residue obtained nickel recoveries of only 50% and, while arsenic and nickel could be precipitated from raffinate separately with hydrogen sulphide, the process was difficult to control and costly.” So states a technical report on the Key Lake mill. The report was prepared by Wright Engineers and Key Lake Mining.
Site operations manager Josef Spross told The Northern Miner Magazine that when the operators were examining nickel recovery potential (some time in the early part of this decade) nickel prices were depressed (about $2 (us) per lb). Today, nickel is fetching better than $6.
The nickel has been disposed of in the tailings pond. The ore also contains molybdenum. A separate circuit is being built now by Northern Shields Construction to remove the moly, which had been left as a contaminant in the yellowcake. A NATURAL SMELTER
It’s been burning for 17 years. Nevertheless, people at Brunswick have all but forgotten the fire in the 3 and 10 stope area. When a 60-m stack wa s built in 1980 to exhaust the sulphur dioxide gas from a stope on the 250 m level, there was no longer a constant nasal reminder that a molten mass of sulphide rock was slowly oxidizing in the stope. But some people, other than the odd geologist, are curious about what’s going on inside the stope.
Brunswick has been monitoring the emissions from the exhaust stack while keeping a close watch on temperatures on the more than 16 bulkheads installed underground to contain the fire. And using a few thermodynamic equations, one engineer was able to estimate when the fire might burn itself out. Based on the amount of sulphides believed to be in the stope, the engineer estimated that in five to six years the stope might be cool enough to open up for a close look.
What is inside once it cools off is anyone’s guess. But it might be a sizable, coarse-grained oxidized deposit, perhaps with significant amounts of native lead, zinc and copper, something that could potentially yield higher recoveries than those achieved treating the fine-grained volcanogenic sulphide ore the company mines. Trouble is, the deposit isn’t big enough to make Brunswick take a serious enough look at it. It probably will remain a mere curiosity. OIL IN SUDBURY?
Keen observers in the Sudbury-area town of Levack will have noticed an oil drill rig (a T-5 Drillmaster to be exact) operating near Inco Ltd.’s McCreedy West mine early last spring. But the reason the rig (operated by Underwater Gas Developers of Calgary) was there wasn’t because Inco was drilling for oil.
No, the company was drilling two large, 12 3/8-inch- diameter holes through gravel overburden to two stopes on the 350-ft and 900-ft levels of the mine. The holes were then used to test the idea of pouring dense, alluvial backfill (82% solids) directly into the two stopes. (Underwater Gas has been contracted because of its accuracy in drilling.)
Previously, Inco had used hydraulic backfill (68% solids) to fill the stopes mined by vertical crater retreat methods. That method of backfilling stopes is expensive. Because of the high water content of hydraulic backfill, each mined-out stope had to have an elaborate bulkhead constructed at the drawpoint to the stope and a stiff, 10-parts- sand-to-one-part-cement mixture poured to plug the bottom of the stope. The water in the stope then had to be decanted and that water removed from the mine.
The large volumes of water added to the costs of underground road maintenance, sump clean-up and pumping.
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