No. 6 shaft, Centennial Mine, Centennial Heights, Calumet Township, Houghton County, Michigan, USAi

Regional Level Types
No. 6 shaft	Shaft (Abandoned)
Centennial Mine	Mine (Abandoned)
Centennial Heights	Unincorporated Community
Calumet Township	Township
Houghton County	County
Michigan	State
USA	Country

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The story of the Centennial Mine began in 1863 when the Schoolcraft Mining Company was organized to work what would turn out to be the northern extension of the Calumet conglomerate lode. Initial work atop the soon-to-be-discovered conglomerate was minimal, and the company would only expend a small sum during this time. However, work quickly expanded with the discovery of the conglomerate lode and the subsequent development of the highly profitable Calumet and Hecla Mines to the south in the later 1860s. Though much like what the Osceola Mining Company would eventually find to be the case at the southern extension of the conglomerate, the Schoolcraft Mining Company, only after expending a fortune, would come to realize that the northern extension of the conglomerate was just as unprofitable, and by 1873, they were forced to shut down due to a lack of funds. The mine was then leased to Capt. William Harris, who, too, would expend a considerable amount of money in what he believed could be a profitable mining venture. However, like the Schoolcraft, he would also fail to turn a profit, and in 1876, the property was liquidated and reorganized as the Centennial Mining Company. Centennial would work the property on and off through the mid-late 1890s before again going bankrupt. Little attention was given to the conglomerate during this time, however, as most of the company’s effort would be focused on sinking two additional shafts on the newly discovered Osceola amygdaloid lode, which initially showed great promise. In 1896, following bankruptcy, the Centennial Mining Company was reorganized as the Centennial Copper Company. Up to this point, a total of seven shafts had been sunk along a nearly three-quarter mile stretch of land atop the conglomerate. The Copper Handbook, published in 1902, states that shafts 1, 2, 5, and 7 were shallow, while shafts 4 and 6 were of considerable depth, and that shaft 3 in particular was one of the deepest in the world, “having been put down 3,200 feet on the dip of the lode.” Despite having been thoroughly explored by this point, and more often than not, deemed unprofitable, the newly formed Centennial Copper Company would make one final attempt to work the conglomerate in 1897. The number 6 shaft, which was 500 feet deep at the time, was extended 700 feet, and considerable drifting was done. Although occasional, rich ore shoots were encountered in the drifts, long stretches of barren ground made the mine unprofitable, and all efforts to mine the conglomerate were abandoned. Work on the two shafts previously sunk atop the Osceola lode was also resumed during this time, but it too was short-lived, and by 1901, the company had shifted all efforts to opening the much more promising Kearsarge amygdaloid lode. They would work the highly profitable Kearsarge lode through 1923, when the Centennial Copper Company, along with many other mines in the area, merged with the Calumet and Hecla Mining Company to become the Calumet and Hecla Consolidated Copper Company (C&H). C&H would continue to work the Kearsarge lode at Centennial until 1931, when low copper prices forced the mine to close. C&H would later resume operations along the Kearsarge lode at Centennial in 1944 and would operate the mine through the mid-1960s, when high production costs and lower grade ore forced the mine to close permanently.

In the early 1950s, following the outbreak of the Korean War and recognizing a northeasterly trending mineralization in their conglomerate mines to the south, C&H set about on a project to dewater and hopefully reactivate the old Centennial Mine workings atop the conglomerate. Fueled by a government contract that guaranteed against a capital loss, dewatering and rehabilitation efforts were begun at the number 3 shaft. Once completed, exploratory drifts were driven northward from six levels of the shaft, and ore grade was found to increase in the lower levels of the mine. In 1964, the decision was made to bring the mine into production. The No. 3 shaft was subsequently deepened to the 36th level, and a drift was driven northward approximately 2,300 feet. From here, the modern No. 6 shaft was raised to the surface at a 38-degree incline. The mine, however, was never fully developed, as labor-management disputes during the late 1960s would result in the complete shutdown of mining on the peninsula.

In July 1972, the Homestake Copper Company, a subsidiary of the well-known Homestake Mining Company, reached an agreement with Universal Oil Products (who had purchased C&H in 1968) to lease their mineral holdings, on a royalty basis, and explore for minerals. Following this agreement, they would form a joint venture with American Copper and Nickel Company, Inc., a subsidiary of International Nickel Company, and set about on a project to deepen the No. 6 shaft in hopes of intersecting the historically rich Calumet conglomerate. They hoped that, with sufficient size, it could support a 5,000 to 10,000-ton per-day mining operation. Homestake would retain 60 percent of the venture and act as manager of the exploration and development program, nicknamed the Key Project.

The initial phase of the project began in April 1973 with the dewatering of the mine’s underground workings. As the pumps had already been shut down for two years at this point, surface run-off water had found its way into the workings, flooding the mine up to the 27th level. Dewatering was accomplished over a three-month period with the use of two skips operating in the No. 6 shaft. During this time, some 53,000,000 gallons of water were bailed from the underground workings. As the water was removed, the shaft and underground workings were rehabilitated. Timber supports were tightened, and loose rock was removed from the backs and walls of the mine openings. Air and electrical lines were also installed to accommodate the needs of lower mine levels that had yet to be driven. By late September of that year, the mine was completely rehabilitated, and the next phase of the project was ready to take shape. The shaft would now be extended to approximately the 45th level. This would involve sinking the shaft a distance of some 1400 feet from its current deepest point. Additionally, Randy Sabo, author of the 1975 book Homestake Search for Red Metal, states:



The shaft was deepened at a rate of 100 to 130 feet per month using a drill and blast method, and by December 1975, the inclined shaft was nearing 6,700 feet (approximately 4150 vertical feet). It was hoped that the 7,700-foot mark (also known as the 55th level) would be reached by September 1976, but shaft sinking would ultimately stop at the 50th level due to low copper values below the 48th level. Drifting would continue northward from the 50th level, but to no avail. Several holes would also be drilled, including two that were planned to intersect the conglomerate about 5,000 feet north of the shaft and about 1,000 feet below the 50th level. Although one showed promising signs of copper, the others were disappointing and only showed areas of very low copper values. Operations would ultimately cease in November 1976 due to low copper prices and the completion of the exploration objectives. In 1977, the pumps were shut down, and the mine was allowed to refill with water. The objective of finding a native copper deposit that could support a larger operation did not come to fruition.

The mine would sit idle again until the late 1980s, when Michigan Copper Co. Ltd., a joint venture of Peninsula Copper Industries, Keweenaw Copper Co., and Torch Lake Holdings Co., would dewater the mine in preparation for full-scale production. The Toronto-based company Great Lakes Minerals would end up purchasing 100% of the Keweenaw Copper Company, who at the time owned 50% of the Michigan Copper Co., announcing that they expected “Centennial, with an estimated mine life of eight years, to enter production in the third quarter of 1991 at an annual rate of 8.5 million lbs of copper in concentrate” (The Northern Miner, 1990, Great Lakes boosts interest in Michigan copper projects). However, nothing would come of this, and operations ceased by the early 1990s. No mining activities have taken place at the No. 6 shaft since. The Highland Copper Company would commission a technical report on the mine during their exploratory work in the Keweenaw during the 2010s, but would ultimately rank the mine as the lowest exploration priority due to the low quantities of copper found during the Key Project. Today, many of the structures that remain at the site of the No. 6 shaft have been given new life by a local manufacturing business. Two other businesses also occupy lots just adjacent to the dry house.

The structures that remain at the site are privately owned and off limits to visitors, but can be viewed legally from Centennial #6 Road.

Mineral List

10 valid minerals.

Rock Types Recorded