Teething problems over at Mascot mine

It’s fair to say that Mascot Gold Mines’ Nickel Plate project near Hedley, B.C., has endured its share of teething problems. But for most new mines that’s all part of growing up — the school of “hard rocks” you might say.

But the mine appears to have turned the corner after a difficult start-up period. Although gold recoveries are still slightly below forecast, steps are being taken to improve this and several other aspects of the operation. The company has initiated a $9.8-million capital program to reduce operating costs and increase mill throughput above planned capacity, Paul F. Saxton, president, told the annual meeting. The capital program, which includes the installation of a gyratory crusher, a hopper pre-clarifier, three additional drum filters and some effluent treatment equipment, is scheduled for completion in June, he said. A change in effluent treatment procedure is being studied because of the high cost of hydrogen peroxide.

The Nickel Plate mine produced 26,609 oz gold and 13,834 oz silver from 213,500 tons of feed during the three months ended Dec 31. The average head grade was 0.14 oz gold per ton and he confirmed that gold recovery was “only a point or two below design objectives.”

Saxton conceded that pressure clarifiers have been a problem in the plant. Because they are getting too much solids through the drum filters, the clarifiers have been unable to handle the solution coming from the filters, so Mascot is changing to a hopper pre-clarifier which should generate a clearer solution for the pressure clarifiers. “This hopper clarifier is used quite extensively in South Africa and, in fact, some places use it without any pressure clarifiers behind it.”

Saxton said that pressure clarifiers are a “little bit new,” and he noted that Pegasus’ Montana Tunnels project “got rid of theirs right away.” Mascot doesn’t have that option because it doesn’t produce a concentrate. “So what we are doing is making them work,” he explained.

The problem caused lower recoveries and created a bottleneck in the plant. “So instead of running at our design rate of 2,700 tons we were only able to run at 2,400.” The jaw crusher has also been a bottleneck because the crushing plant has to be run seven days per week 24 hours per day to maintain production. Saxton said the company would like to run the plant five days per week 12 hours per day so a gyratory crusher will be installed. “By doing this, not only do we get it done quicker and cheaper but we can handle the larger pieces of material that come to us.”

Mascot hasn’t had any problem supplying the mill from its open pit operations; although head grades for the quarter ended September, 1987, were about 0.086, (N.M., Feb 8/88), Saxton argued there was a good reason for this. Lower grade material was fed into the mill for tuneup purposes which is common to most new milling operations.

“This month we are planning to run 0.2 oz and it’s coming into line very well. We have been averaging an 86% recovery rate and it’s moving right along,” he said. At present, the mill is handling about 2,500 tons per day and operating costs are approximately $300(C) per oz. This should drop to below $200(US) by July, he predicted.

In the 1988 fiscal year, Mascot anticipates gold output will be approximately 130,000 oz which includes a small leaching operation. Saxton said the company is retiring its gold loan (100,000 oz) ahead of schedule and he added: “Our thinking is that we will take down 57,000 oz either in dollars or in gold. We have the option to do it either way.”

The company has sold 32,500 oz forward through February, 1989, at a minimum $470(US) per oz which is just under 28% of projected production for the current fiscal year. And Saxton confirmed that additional forward sales are being contemplated. Mascot expects to take down 57,000 oz of the gold loan this year in either dollars or gold. “We have that option to pay back in dollars or in gold,” he said. The mine should be on line for accounting purposes in the second quarter.

Mascot is planning a major exploration program at its Bralorne mine property this year. “If our plans go as well as we anticipate, we would expect to bring the mine into production in 1989,” he said. An earlier study estimated capital costs for the project at $14 million for a 300-ton-per-day milling operation and a yield of 30,000-40,000 oz per year. Mining would take place above the 800 level and there are 150,000 tons grading approximately 0.4 oz gold that could be mined initially to speed up payback.