Lac’s second Bousquet mine More tons, better grade

An initial ore reserve figure of 7.8 million tons grading an average of 0.187 oz gold per ton has been established by Lac Minerals from a new zone near the eastern boundary of its Bousquet property in northwestern Quebec.

The possible ore reserves — more tons and better grade than published reserves at the 7-year-old Bousquet mine currently in production — could lead to a much larger capital expenditure on the project than originally expected.

The Lac discovery (N.M., June 30/86) is shaping up as another mine for Lac — it has already dubbed the deposit Bousquet Mine No 2 — and, although results of a feasibility study are not expected until March at the earliest, a new shaft and mill are being considered for the property.

Dumagami Mines, which holds the property adjacent to Lac to the east, says it also has about seven million tons of ore indicated on the same deposit but on its side of the property boundary. When combined, the two reserve figures add up to one of the largest deposits in Quebec.

Lac and Dumagami have combined to drill a hole on their common boundary, a joint venture that is currently under way.

“It’s getting bigger and better all the time,” says Dumagami’s secretary-treasurer Barry Landen.

Dumagami has already accessed the zone at the 700-ft level from its existing shaft about 1,200 ft from the western boundary. It is now deepening the shaft to 3,200 ft and plans to drive to the new deposit on the bottom two levels.

Mr Landen says Dumagami plans to start production on the deposit in 1988.

The Lac discovery is considered by Dumagami to be the extension of the deposit which it discovered by deep drilling in early 1986. Lac started looking for the extension on its side of the boundary after seeing those drill results, says Dumagami.

Dumagami’s published reserves to date indicate 3,146,000 tons on the new zone grading 0.164, but Mr Landen says reserves on the entire property are in the order of seven million tons. That would include a lower grade zone which Dumagami originally planned to mine. Low gold prices since the shaft was first put down and the low grade conspired to prevent the company from ever getting to production.

Dumagami feels its original low grade zone and the new deposit are the same structure separated only by an area of sub-economic grade mineralization.

The shaft for Lac’s Bousquet No 1 mine, a mine which produced 46,492 oz of gold in the first nine months of 1986, lies about 1.2 km east of the new deposit. In September The Northern Miner reported that the new deposit might be accessed from the third and seventh levels of the No 1 mine, but the feasibility study will address the question of whether to drive west to the deposit on those levels or sink a new shaft.

The deposit’s name indicates Lac is leaning toward a new shaft.

And although that in itself would involve a hefty capital investment, a mill for the property has not been ruled out. Ore from the Bousquet No 1, about 1,750 tons a day, is currently trucked 25 miles to the Terrains Auriferes mill.

If the new deposit does shape up as a second Bousquet mine, a mill on the property for both mines makes sense. However, the Terrains Auriferes mill has performed well for Lac and the company is unlikely to close it. In the company’s 1985 annual report, its most recent, the company reported an increase in throughput at the mill and a 12% reduction in milling costs to $11.28 per ton.

At Lac’s East-Malartic mill, by comparison, milling costs were $12.63 per ton in 1985.

The possible reserves are substantially better than proven, probable or possible reserves at the Bousquet No 1. At the end of 1985, the No 1 had about 4.0 million tons of proven reserves grading 0.141 oz, 700,000 tons of probable reserves grading 0.160 oz and 1.3 million tons grading 0.166 oz. (The company does not include in those reserves some 4.4 million tons grading 0.061 oz and 6.3 million tons grading 0.062 oz in an open pit zone at the No 1 mine.)

While the No 1 has suffered some fairly severe ground control problems, the new deposit is reported to be in much more competent ground. The ore reserve estimate is calculated above the 3,300-ft level.

Vice-president exploration Dennis Sheehan is “very confident” of the reserves, says a company spokesman, and drilling is continuing with three drills at the new deposit and at the No 1 mine to probe the extension of the ore at depth.

In fact Lac is in the midst of a total reassessment of the entire Bousquet property.