Canadian Rockhound: The Craigmont Mine, British Columbia

The Craigmont Mine was developed during the mid-twentieth century, on the southeast slopes of Promontory Hill in the Nicola Valley near Merritt, British Columbia. It is of particular interest to the collector because of the variety of metallic and precious metal minerals it has produced. The mine itself has had a short, but interesting history. This article will introduce the mineral collector to the mine, its operations, and some of the ore minerals found there. The geology and mineralogy of this locality may warrant further exploration by collectors to locate sources for potential mineral specimens.

Geological Summary

Over 225 million years ago, during the Triassic Period, the Nicola Valley was covered by thousands of feet of volcanic rock. From the geological record, waves once lapped at the sides of Promontory Hill, which was situated next to the inland sea that covered most of Canada at the time. It is not possible or relevant here to discuss the many complex geological events that occurred in the region over the next 200 million years, such as the collision of terrains, local erosion, and the formation of the Columbia and Canadian Rocky Mountain systems. However, it is the more recent geological events that played an important role in exposing the ore-bodies in the area. Approximately one million years ago, during the ice age of the Pleistocene Period, glacial ice gouged away some of the lava that covered the Craigmont ore-bodies, leaving behind a layer of gravel that partially filled the Nicola Valley and upper slopes of Promontory Hill. At one time, two meters of gravel actually covered the highest outcrop of the ore body.

Ore Minerals

The original ore body consisted of a variety of minerals, including precious metals. Minerals recovered included magnetite (Figure 1), iron, pure copper (Figure 2), silver, gold, along with significant chalcopyrite and specularite, hematite (Figure 3), bornite (Figure 4), calcite (Figure 5), orthoclase, garnet, epidote, amphibole, tourmaline, diopside, and malachite (Figure 6).

Figure 1. Magnetite.

Iron
Figure 2. Pure copper.

Figure 3. Specular hematite.

Bornite
Figure 4. Bornite. Calcite
Figure 5. Calcite.

Figure 6. Malachite.

Mining History and Operations

The ore-bodies were discovered during the early 1940's. The location of the Craigmont Mine was ideal for ore shipment. The mine was just 15 km northwest of what is today the city of Merritt, and 200 km northeast of Vancouver. Elevation in the area runs from 565 m at the Nicola River to 1,734 m at the summit of Promontory Hill. The mine covered a total of 7,000 acres.

From it's beginning in 1961 the Craigmont Mine added over 426 million kilograms of copper to the world market and grossed over $450 million in sales (Figure 7). Production costs including wages were $112 million. The Craigmont's net earnings over its life span were $115 million and paid its shareholders $107 million in dividends. Both the federal and provincial governments received $74 million in direct taxes and royalties. In February 2000 the mine ceased operation as a consequence of the falling price of copper. Over 5,000 people were employed at the Craigmont between 1946 and 1983. In 1983, Pinecrest Gold Mines Ltd. was formed and the Craigmont Mine was terminated. At one time, there were 660 people employed during its peak operation. By 1977, the annual payroll had reached $7,193,000.

Craigmont open pit
Figure 7. The Craigmont's open pit operations in the beginning.

The Craigmont can take full credit for instigating BC's first large-scale open-pit mine. During the early 1960's, the Craigmont could extract up to 50,000 tones of copper ore per day. This amount could provide a continuous feed to the mill of 5,560 to 6,670 tones per day, and a stockpile that would help to carry the mine during the changeover to underground mining. When the Craigmont introduced a new mining system, called the "sublevel caving method," which was previously developed in Sweden, the entire mining system worked well and it equaled or surpassed other copper mines around the world (Figure 8).

Craigmont underground workings.
Figure 8. Underground workings of the Craigmont mine.

During the time of Craigmont's operation, it spent an additional $8 million on exploration to search for other ore bodies nearby. By early 1960, the company had identified three separate ore bodies with an estimated 22,575,000 tons of ore that would average 2.08% copper and 19.6% iron. On the 2,400-foot level, 4,000 tons were mined per day. Between June 1960 and March 1961, a total of 3,555,000 cubic yards of overburden (glacial till) had to be removed before open-pit mining could be begun. The Craigmont now had to obtain power from BC Hydro. A 60,000-volt transmission line from Merritt to the Craigmont (17.5 km long) was constructed to transport 5,000 kilowatts of power. At that time, this was the largest industrial load on BC Hydro's mainland system.

Now came the task of transporting thousands of tones of ore down the steep mountainside (Figure 9). Underground ore-passes were eliminated due to expense, construction time and winter conditions. A cable supported belt system was built measuring 1,740 meters and 76 centimeters wide, with a fall of 342 meters. A 4-centimeter diameter steel cable supported and drove the belt. Power to turn the cables came from a 370 hp electric motor, thus enabling the belt to carry 360 tons of raw ore an hour. This whole system cost (at that time) $400,000.

Figure 9. Conveyor belt.

Another valuable commodity the Craigmont had to offer, besides it's copper, was magnetite. Coal producers use this mineral as an essential component in their heavy media separation process. At the time (December 1969), the Craigmont mine was capable of producing 75 tones of Magnetite per day. By November 1970, the Craigmont produced 17,331 tons (15,614 tones) of high-grade magnetite concentrate. In 1971, the recovery circuit was enlarged to a capacity of 50,000 tons (45,000 tones) per year. Today, while inactive in copper production, the mine still extracts and transports 80,000 tons of magnetite per year (Figures 10 and 11). In March 1982, the last copper was mined from the Craigmont. The entire milling operation was switched over to processing magnetite, and it continued processing magnetite ever since.

Figure 10. The Craigmont's open pit today.

Crusher
Figure 11. Crusher (far background), ore bins and burned out weigh scales.

Initially the Craigmont's ore reserves were based on 22,575,000 tons, which averaged 2.08% copper. This worked out to 939 million pounds of copper. In the end, the Craigmont mined 36,750,000 tons of ore at an average of 1.28% copper. Today the Craigmont refines just the magnetite that had been stockpiled, and is expected to remain in operation for the next 15 years.

The reality is that no mine can continue producing forever. M. Shewchuk, the author of "The Craigmont Story", writes:

"Mining is an industry that deals with a finite resource. The life of a mine is determined by the size and the nature of the ore body and the ability of men and women to extract the minerals profitably."

Mineral Collecting

I was granted permission from the Craigmont Mine to conduct collecting tours for the 2001 season, and I look forward to visiting this mine. The Craigmont may provide collectors with some interesting specimens, and further exploration of this locality would help determine whether sources still exist. Additional information about the mine and mineral specimens is welcome.

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