Mascot a text book mine

You can learn a lot about a mining operation by listening to employee discussions in company lunchrooms. In most cases the conversation is fairly predictable: complaints about co- workers, equipment problems and a litany of related gripes which are common to all mines.

But more often than not the lunchroom conversation at Mascot Gold Mines’ Nickel Plate project involves the price of gold and its impact on the company’s stock. The reason for this is simple. Employees are encouraged to participate in the company’s stock purchase program and most of them do.

The Mascot project is a textbook example of equity participation from exploration right through development. Flow-through funding was utilized to delineate the open pit potential of the property — and President Henry G. Ewanchuk concedes there probably wouldn’t be a mine there today without it. (Are you listening Michael Wilson?) Mascot poured its first dore bullion April 24 and since that time has been overcoming normal startup problem s which all new mines encounter. On a recent visit to the property the company was in the process of stabilizing feed to the mill after encountering some near- surface oxide material. While sometimes higher grade, the oxide ore slows filtration so it’s had a detrimental but temporary impact on mill throughput.

Commenting on its effort to provide a more uniform feed, mine manager Jim Walmsley said the plant has actually reached target capacity and one day the crusher handled 5,600 tons of feed. At the moment the company is keeping the grind coarse and feed is being supplied from the South and Central pits.

Mine superintendent Al Bellamy said the mining rate was about 26,000 tons per day with an approximate 8.5-to-1 strip ratio. Actual mining commenced the second week in October although ramp development was under way before that. Pointing out that “higher grade pits” are being mined initially, he said there are about 1.5 million tons of reserves in the South (Bulldog) and Central pits which will contribute to a faster payback. Reserves 8.3 million tons

Proven open pit reserves are 8.3 million tons grading 0.14 oz gold and the possibility of increasing reserves is excellent, the company confirmed. The present cutoff grade is 0.05 oz gold but this will drop to 0.03 oz in a few years. Chief geologist Bill Wilkinson noted that Mascot’s exploration grid was 100 ft by 100 ft (staggered) and he concluded they are actually finding larger amounts of ore than was “projected from the underground workings.”

The ore zones extend more than 5,000 ft in a north-south arc along the easterly slope of Nickel Plate mountain; the gold is contained in a 500-ft-thick skarn about 200 ft of which contains favorable beds, said Mr Wilkinson. Mining will move to the North pit (which will be the largest) about a year from now.

Underground mining operations ceased in 1955 but Mascot still has to contend with old workings which often require some innovative backfilling techniques. Track and timber have been stripped from specific areas underground and drop raises have been drilled into old stopes to deliver backfill. “We have broken into the underground and have collapsed one stope already,” he noted.

Mines in Ontario and Quebec which claim to have hard ground and think there isn’t any in Western Canada had better take a second look at Mascot. The ore has a bond index of 19 kwh per ton and to liberate the gold a grind of 80% passing 400 mesh is required. Ore grade material is hard and abrasive and conventional tri-cone roller bits have been known to disintegrate after a few hundred feet, Mr Bellamy said.

Because of this, the company is using button bits and down-the- hole hammers with high pressure, screw-type air compressors for increased penetration. The track- mounted Ingersoll Rand DM 45E drills are “quite manoeuvrable,” he pointed out. A staggered 10-ft- by-10-ft drill pattern is used and a 1-lb-per-ton powder factor which is quite high by open pit standards elsewhere in B.C. Emulsion-type explosives are utilized exclusively because of their rapid detonation velocity; ammonium nitrate and fuel oil (ANFO) is too slow and its gas-producing nature provides too much throw, he concluded. Meticulous sampling

Mr Walmsley said the operation has adopted meticulous sampling techniques to control grades in the pit. Automatic samplers gather representative material for a 10-ft length of drill hole and 500-550 assay determinations are made by atomic absorption each day. Bulk sampling of drill holes is done for correlative purposes and results are cross-checked by fire assay technique s both on and off site. Needless to say the company’s large assay facility is kept very busy. Also, most metallurgical test work is done on site.

With the current 8.5-to-1 strip ratio, drilling is a “No 1 priority,” said Mr Bellamy. So about 2,600 ft is required each day (seven days a week) to maintain production.

In general, the Mascot orebodies contain finely disseminated gold and large quantities of arsenopyrite and pyrrhotite. The ore has a blocky nature suited to autogenous or pebble mill grinding which was a key consideration in flow sheet design for the mill. Two-stage crushing is used followed by conventional rod, ball, and pebble milling to ensure property mesh size. Two- and 4-in-size pebbles are screened out in the crushing plant for use as grinding media.

Cyanidation techniques have been found to yield optimum gold recoveries with grinding to 400 mesh. The gold is then precipitated from solution with the Merrill- Crowe zinc dust process and the final product is dore bullion. Mill superintendent Don Ingram emphasized that Mascot has employed “standard technology” in the mill, adding that some of the equipment was purchased second-hand and refurbished to save money.

During our visit, mill heads were averaging about 0.1 oz gold per ton and throughput was below the 2,700-ton-per-day desired rate because they had encountered oxide material and were attempting to blend it. “We don’t have much surge capacity in the system and are just balancing the circuit out,” he added.

Where practical, mine employees have been hired locally and many of them commute daily from places like Kelowna, Penticton, Keremeos and other centres in the north and south Okanagan. Maintenance superintendent Bob Trent said the company was able to hire top-notch tradesmen, which bodes well for the operation. The mine is non-unionized and there is no trade demarcation and subsequent loss of productivity.

The project has proven to be a remarkable exploration success and no doubt will turn out to be an exceptional mining success too. For a mine which not that long ago was viewed as a potential underground producer it has come a long way.