American Barrick’s wholly-owned Camflo mine 12 miles west of Val d’Or, Que., rates but one page in the company’s 62-page, 1987 annual report. Barrick’s Mercur and Holt-McDermott mines and the Nevada gold vault known as the Goldstrike property, which have a lot of people singing the praises of Barrick President Peter Munk and company, have overshadowed the sturdy, reliable Camflo. But it’s up there in mosquito country, on the Quebec end of the Golden Highway, producing roughly 31,000 oz a year. It adds a steady $18 million or $20 million a year to Barrick’s coffers. While Barrick’s thinkers at the Toronto head office ponder the right combination to unlock the 15-million- oz Goldstrike vault, no-frills Camflo, a low-cost producer, chugs along, its role in Barrick diminished but not forgotten.
The first headframe to stand over the Camflo shaft was a wooden one bought second hand in 1964 from a nearby mothballed producer. All the mill equipment was also “bought cheap,” according to Alex Makila, a former assistant mine manager and currently chief geologist. Capital costs totalled the meagre sum of $1.5 million to establish the mine. The mill, for another $1.5-million outlay, was built a few years later after the mine had proved itself. Of course, this was back in the mid-1960s when a dollar was still almost a dollar, and it cost Camflo only $21.57 to mine and mill an ounce of gold. The average millhead grade back then was 0.3 oz gold per ton. The mine was producing roughly 90,000 oz a year. Today, comparable costs are $314(C) per oz (mined and milled) with an average millhead grade of 0.085 oz gold per ton, which works out to $337 for each ounce produced.
As the shaft went deeper, a steel headframe was superimposed over the wooden structure. The steel one was also a garage sale special. The shaft went down to 900 ft initially and, as underground development progressed at depth, it was extended in stages to its current 4,065 ft. The mine has 24 levels in total, with 17 levels in operation now. The shaft has three compartments to the 13th level. A fourth compartment was added below that.
Two, 6-ton skips, hoisted by a Dominion Engineering 10-ft, double drum hoist, bring up mine ore and waste. New Ingersoll-Rand air compressors supply the mine air. Camflo has three underground crushers, all Allis Chalmers-made and located at the 3750, 3000 and 2500 levels. That allows mining at a 2,000-ton-per-day, 5-day cycle and sustains a daily 1,350-ton feed into the mill through a 7-day week.
“The cardinal rule at this mine is never let the mill run out of ore,” said Mine Manager Richard Mailloux. The mill hasn’t stopped running since 1969.
Our tour, conducted by Mailloux, whose father was a former Camflo mine manager, and spare mine captain Jean-Guy Cote, started at the 3650 level in a ventilation drift that was being driven to prepare new ground for mining. (At this level, the deposit is entirely on ground held by Malartic Hygrade Gold Mines. The two companies mine this portion jointly. Details of the agreement are given below.) The 8×9-ft drift was drilled out with jack legs and mucked by scrapers. This is not the type of mine where jumbos can work. All such development drifts advance at the rate of 8 ft per shift.
Still on 3650, we viewed a drawpoint where an Atlas Copco mucking machine (the mine also uses Eimco- Jarvis Clark mucking machines) was loading a car. On average, muckers can load 30 to 35 cars per shift. Generally, ground control is not a difficulty at Camflo, but in the lower levels, where stresses increase, more ground control techniques are required. For stability, the drawpoint was ringed with concrete and corrugated steel. Mailloux said the company does install cable to hold the hangingwall and that it uses rockbolts and screening on the backs of drifts, but the sides are secure enough.
At a former haulage drift on 3150, a miner was drilling off a longhole stope with a 2-inch-diameter Atlas Copco BBC-120. Only two of the machines are in use now, but Mailloux said they are planning to add one more later on. At one time, five longhole drills were in use but, after the machines had drilled off 1.5 million tons preparatory to blasting, they weren’t needed. The porphyry plug that carries most of the ore-grade material mined by long hole was 45 ft at its widest point in this particular drift.
The current drilled off reserve is roughly three-quarters of a million tons. (To put that in perspective, Camflo milled 372,294 tons last year.) A 1.5-ft-long steel casing is slipped into the hole to secure the collar, while the rest of the hole is left open until the stope is blasted. The holes have never pinched because of pressure, according to Mailloux.
Camflo is fortunate among the mines along the Golden Highway, because most of its production muck comes from the less costly long-hole method. The mining method is standard. Levels are established at each 150-ft interval (in the deeper portions of the mine they are cut at 175 ft). A crosscut at each level is driven north to the ore and an east-west drift is established along the footwall. At 50-ft intervals, diamond drills outline the ore zones. Two or more drawpoints are excavated on the bottom, or haulage, level and raises are driven to the next level. Sub-drifts are driven off the raises at 40 ft (the sill sub) and 100 ft (the drill sub) above the bottom level. From these subs, diamond drill holes outlined the ore at 50-ft intervals to find the hangingwall and footwall and determine the exact shape of the stope. For long-hole mining, the standard drilling pattern is 3 ft between rings with the holes spaced 11 ft at the toes. (The mine staff, under the supervision of Cote, designed and built four drill rigs on skids with hydraulic extendable jack bars, which has taken some of the bull work out of setting up the drills.)
From the 3650-level drawpoint, a mucker was drawing out 115,000 tons of ore from a 150-ft-high, 75-ft-wide and 200-ft-long stope. That’s quite a generous stope size for a Golden Highway mine. The mines along the highway from Timmins, Ont., to Val d’Or, Que., are predominantly narrow- vein operations.
This method also accounts for the unusually low-grade millfeed at Camflo, which runs at 0.08 to 0.09 oz gold per ton. “That’s mainly because of the mining method we use,” Makila said. “We use long-hole stoping with no backfill at all. The dilution coming from the mined-out stopes on the upper levels with today’s gold price can be milled at a profit. The mixing of this dilution with the regular mine muck lowers our overall grade. But it also lowers our overall mining cost.
“We really have to work at things today. In earlier days, we had 1,500 to 3,000 tons per vertical foot. Now we have 500 tons per vertical foot.” Where the zones are less than 16 ft wide or where the margins of the larger zones are irregular, shrinkage stopes are started. Usually, odd shaped veins, slots for long hole stopes and fringe stopes along the ends of the orebodies are mined this way, using Secan 240 and 250 jack legs. If some of these stopes prove to be sub-economic, they are abandoned. However, many contain more ore than expected and these are converted to long-hole stopes.
In fracture zones, rib-and-pillar stoping is the preferred method. While the costs rise about 25% above the costs of long-hole and there is a lower tonnage, it is still economic to retrieve the material, which is a diorite ore dipping about 40 . “Sometimes if the ground is good, we’ll drill off the pillar too. When you leave the pillar you leave 25% of the ore,” Makila said. Waste and ore is hauled in 96-cu-ft Granby cars attached to Clayton locomotives. Exploration
Most of the ore that has been mined at Camflo comes from a porphyry monzonite plug, an oval, pipe-like plug dipping 65 north that in plan is roughly 300×600 ft. (For details, see accompanying story on the geology of Camflo). The porphyry ore can be as wide as 130 ft and as long as 400 ft. According to Makila, the plug is unique to Camflo and extends onto the adjacent Malartic Hygrade at depth. Most other mines in the area are vein-type deposits.
Camflo is exploring outside the area of the plug. In July, 1972, Camflo and lac Minerals entered into an agreement to explore the Willroy property, to the east of the Camflo ground. To the west, on ground held by Barrick, Malartic/ Hygrade and Consolidated nrd Resources, an exploration program is in the works.
On the western portion of the Camflo property underground, a crew is driving a drift on the 750 level along a fault outside the porphyry plug that carries ore-grade mineralization. It was an old area that had been worked before, so Camflo decided to extend the drift to check for a continuation of the vein. After 150 to 200 ft of drifting, miners picked up the fault again. Continuity at a deeper level was confirmed by driving along the 900 level and raising up to 750. More raises are planned to further define the ore-bearing fault and the drifting will continue until the vein peters out. A surface diamond drill hole also intersected the fault at the 1100 level. Other, non-plug targets include sedimentary/diorite contacts on the 1500 and 2400 levels.
Mine planners are also keen on exploring the porphyry plug at depth, but that may require the sinking of a winze. Underground development currently extends to 4,000 vertical ft. Production statistics
In 1987, the Camflo mine produced 29,763 oz of gold from 372,294 tons of ore grading 0.085 oz per ton, for a mill recovery of 94%. (The tonnages and ounces produced reflect only the production that is credited to Barrick’s account. Another roughly 90,000 tons is credited to Malartic Hygrade’s account.) Cash costs per oz were $237 (us). In the first half of this year, 198,614 tons of ore grading 0.098 oz per ton were milled producing 16,851 oz of gold. Cash costs were $259 (us) per oz. Additional underground exploration accounted for the rise in cash costs. Current reserves of 1.1 million tons grading 0.09 oz gold per ton are good for about 3 years of production. Production at Camflo comes from its 100%-owned mine and the portion of the porphyry ore that is mined on the Malartic Hygrade side. Mine operator Camflo receives a 40% share in the Malartic Hygrade production. Costs are shared on the same Malartic 60%/Camflo 40% basis. Ore reserves on the Malartic Hygrade side are 459,485 tons of 0.110 oz gold per ton.
The agreement between Camflo and Malartic Hygrade to share costs and profits was signed in 1980, after a series of on-again, off-again talks that stretched over several years. The porphyry plug begins to cross the property boundary at the 2100 level and the plug is entirely on Malartic ground at the 2800 level. Milling
Crushed ore from underground is -6-inch material that passes through two Symons cone crushers, reducing the material to –3/8 inch. This is stored in three, 700-ton fine ore bins and fed, as needed, to an Allis-Chalmers 8×12-ft rod mill and two Allis-Chalmers (an 8×15-ft and a 9×12-ft) ball mills. The discharge from the rod mill is mixed with the discharge from one of the adjacent ball mills and pumped to two, 15-inch Krebbs cyclones. The discharge from the second ball mill reports to a 15-inch cyclone. The underflow from the three cyclones returns to the ball mills; the overflow is sent for secondary separation to two other 15-inch Krebbs cyclones. The overflow from the secondary cyclones, an 80% -200 mesh slurry, is fed to three thickeners. The overflow from the thickeners is processed through a 42-leaf clarifying tank and Perrin presses after the addition of zinc dust and lead acetate.
The tailings are dumped in a 200-ac pond. The effluent from the pond drains into a retention basin, the water from which is pumped back and reused. About 80% of the water is recirculated. The amount of suspended particulates and cyanides is extremely low in the pond effluent. Downstream of the pumping station, there is no trace of any cyanide and only small traces of soluble metals.
All in all, the Camflo is a clean, tightly-run operation from beginning to end, and though it’s a small feather in Barrick’s cap today, its efficient, knowledgable and dedicated workforce lend an especially fine lustre to Barrick’s overall plumage.
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