TECK CORP. You Can’t Judge a Mine by its Reserves

Published reserves at Teck Corp.’s 100%-owned Beaverdell mine show enough silver ore for just one more year of mining. But don’t write the epitaph for this operation just yet. There has seldom been more than one year of reserves at the mine during its 87 years of continuous operation. During that period, Beaverdell has produced nearly 45 million oz of silver.

Ore production from Wallace Mountain in southern British Columbia, 40 miles from Kelowna and about 30 miles north of the U.S. border, began in 1898 and the mine has been in continuous production since 1900. The first wagon loads travelled 45 miles to the nearest rail line for shipment to a smelter in Nelson, B.C. The high grade ore occurred in narrow, irregular and discontinuous seams. Access to the seams was obtained by adit. The ore was mined, hand-sorted underground, transported to surface and hand-sorted again, and then shipped. This simple practice continued until 1950 because limited reserves precluded construction of a mill.

In 1946 Karl Springer acquired Highland-Bell Ltd. and put together a number of properties on Wallace Mountain which were being high- graded by prospectors. Highland-Bell continued to ship crude ore, but this became less attractive as offsite costs increased and ore grades decreased. In 1950 Highland-Bell built a 50-ton- per-day mill and gradually, over a number of years, the capacity was increased to 85 tons per day. The mill was the first designed by Harold Wright who went on to found Wright Engineers Ltd. of Vancouver. Concentrates were shipped via rail to the Cominco smelter at Trail, B.C.

In late 1969 Teck purchased from Springer effective controlling share interest and management of Highland-Bell and Leitch Gold Mines. The Beaverdell mine was in the Highland- Bell and Leitch portfolio. Teck gradually increased mine production and the mine is now rated at 120 tons per day.

The mine area contains five different vein systems generally striking northeast-southwest and east-west and containing similar ore. The veins occur within a large block of quartz diorite of Cretaceous age. The diorite east of the mine area is roofed by tightly folded and metamorphosed sedimentary and volcanic rocks of the Wallace formation. The mineralized zone is normally quite strong along the contact and persists for short distances, as much as 100 m, into the Wallace formation where it thins out rapidly. This zone is about four miles long and contains the vein systems. The western half contains easterly- striking systems dipping at about 70 degrees . The central part contains the strong northeast-southwest-striking Bell and Lass systems. The strike changes to east-west in the eastern section and the mineralogy changes from silver to copper and gold.

The ore occurs in quartz veins varying from a few inches to 6 ft and averaging one foot. Lean and rich zones alternate. This, combined with severe faulting, makes locating ore extremely difficult. Faults are closely spaced and chop the veins into innumerable sections with dip and strike lengths varying from inches to several feet.

Several minerals at Beaverdell are of primary economic importance. Most of the silver is associated with sulphides, with some native silver. The ore contains galena, sphalerite, pyrite, argentiferous tetrahedrite, pyrargyrite, argentite as well as acanthite, polybasite and dyscrasite. Some arsenopyrite and chalcopyrite occur with pyrite. The ore sent to the mill contains about 1% lead, 1% zinc and 10 oz silver per ton.

The ore outcrops at elevation 4,500 ft. There are eight active adits between this elevation and the bottom adit at 2,910 ft. A decline system permits mining below 2,910 ft to an elevation of 2,800 ft. Internal hoisting is used to move equipment and supplies to various working levels. Level intervals are irregular and average 75 ft. Ore is trucked from the various portals to the mill.

The mine is dry and has a very comfortable working environment. Ground conditions are excellent. Most of the mining is in hard, competent diorite and little timbering or rock-bolting is required. Ventilation is by natural airflow assisted by fans except on the 2,900-ft level. This level has auxiliary ventilation. It is more than two miles long and most of the ore is hauled on this level.

All headings, as well as stopes, are one-man operations; one man goes through the complete cycle of mucking, drilling, blasting and advancing pipe, track and ditch. A 7-ft round is normally taken. Headings are normally 7 1/2 x7 1/2 ft. This is a small underground mine and it is necessary that small mining equipment is used. The mine uses diesel and track 1 1/2-ton locomotives on 18- and 24-in gauge rails. Ore cars have a capacity ranging from one to two tons. Other equipment includes mucking machines, slushers, jacklegs and stopers.

The milling process is relatively uncomplicated. Ore is trucked to the mill, passed over a screen, washed and sorted. About 5% of the waste is removed manually. Ore is then crushed by a 9×16-in jaw crusher and a 22-in cone crusher and conveyed to one of three fine ore bins. The ore from the fine ore bins is fed into a 6×6-ft ball mill and over a jig prior to flotation and filtration.

Each month 60-100 tons of jig, lead and zinc concentrate is trucked to the Cominco smelter at Trail. The lead concentrate contains about 1,000 oz of silver per ton, the jig concentrate about 500 to 1,200 and the zinc about 100 oz per ton. These figures fluctuate considerably depending on ore grade. Silver recovery is 90%, lead 92% and zinc 85%.