After 45 years of operation – Undeveloped reserves at depth assure

Still going strong after more than 45 years of operation is the Campbell gold mine near Red Lake, Ont., of Placer Dome (TSE). This remarkable producer, which was started up in 1944, has recovered 7,075,403 oz. gold (to the end of 1990) from the milling of 10,126,000 tons of ore. The first mill and roaster, rated at 300 tons per day, commenced operation in May, 1949, and over the years capacity has been expanded to the present 1,170 tons per day.

In spite of the major tonnage of high-grade ore that has already been extracted, currently delineated reserves are sufficient to carry the operation at its present level for 13 more years, without any diminution of grade. What the reserve figures fail to tell is that there are still four more levels yet to be driven from the present shaft to tap the downward extensions of the known ore shoots.

Diamond drilling has confirmed several of the ore-bearing structures below the lowest openings on the 23rd level (3,400 ft. below surface) and indeed, below the present shaft bottom at 4317 ft.

Campbell is truly a phenomenal operation and it has long since earned its place, along with the Lake Shore, Hollinger, McIntyre, Kerr Addison and not too many others, as one of the great gold mines of North America.

Oddly enough, the early history of Campbell (its original owner was Campbell Red Lake Mines) and its neighbor, the A.W. White gold mine of Dickenson Mines (TSE), gave no inkling of what the future had in store. Dickenson was the favored company in the earliest of days and the story of these two mines is one of the fascinating ironies of Canadian mining lore.

It is interesting to note that diamond drilling is not only confirming the known ore shoots at depth but recent work on the uppermost levels of the mine is proving the presence of ore-grade material in a heretofore unexplored geological environment. The mineralized areas uncovered to date are limited in extent but the testing is still at the fifth level and much can happen between there and the 27th level, the lowest level from the present shaft.

Campbell’s proved and probable ore reserves to December, 1990, totalled 5.48 million tons grading of 0.559 ounces per ton.

Prior to Dec. 31, 1986, Campbell’s reserves were calculated in a conservative manner and only those tonnages that were proven and could be mined without incurring further development costs were considered to be in the proven category. (No probable category was recognized.)

This method was not perceived as giving a realistic idea of the mine’s potential and a consulting firm was called in to bring the system more into line with current Canadian practice.

The system arrived at was a modification of a conventionally derived proven-and-probable figure by a factor representing the actual tonnage and ounces divided by the theoretical tonnage and ounces of the immediately overlying stope. In other words, an allowance was built into the reserve figures to compensate for the geological peculiarities of the individual ore zone.

In most cases, the factor was greater than one. Unfortunately, the characteristics of the ore zones were not constant nor projectable at the requisite degree of accuracy and as a consequence, as of Jan. 1, 1991, ore reserves have been estimated in the conventional manner: length by height by average width by estimated grade, with no provision for historic variables.

The ore occurs in five principal zones, three of which have been continuous from surface to the lowest levels: A, G and F. The A zone was the initial discovery at surface and is still strong in the lowest levels. The F zone was a major producer in the upper and middle levels but is now practically exhausted. The G zone continues to depth in the same manner as A.

There are numerous other zones of lesser vertical extent.