No. 3 shaft, Centennial Mine, Centennial Heights, Calumet Township, Houghton County, Michigan, USAi

Regional Level Types
No. 3 shaft	Shaft
Centennial Mine	Mine (Abandoned)
Centennial Heights	Unincorporated Community
Calumet Township	Township
Houghton County	County
Michigan	State
USA	Country

The No. 3 shaft of the Centennial Mine was first sunk during the late 19th century by the Centennial Mining Company, on land previously mined by the short-lived and unsuccessful Schoolcraft Mining Company, in an attempt to mine the northern extension of the Calumet and Hecla (C&H) Conglomerate. It was one of seven inclined shafts sunk along a nearly three-quarter mile stretch of land atop the conglomerate, with shafts 1, 2, 5, and 7 reported as being shallow, while shafts 3, 4, and 6 were reported as being of considerable depth. The No. 3 shaft was especially deep at 3,200 feet in length, and at the time was one of the deepest shafts in the world. A crosscut was also driven east from the 31st level to facilitate some mining of the Osceola Lode. Although occasional, rich ore shoots were encountered in the drifts, long stretches of barren ground made the mine unprofitable. Even after the company was reorganized as the Centennial Copper Company in 1896, the mine would end up closing in 1898 as the company shifted operations to the nearby Kearsarge Lode. In 1923 the Centennial Copper Company, along with other mines in the area, merged with the Calumet and Hecla Mining Company to become the Calumet and Hecla Consolidated Copper Company.

It wasn’t until the 1950s when Calumet and Hecla began to notice a northeasterly trending mineralization in the C&H conglomerate mines that they decided to dewater the old Centennial Mine workings to the north. ”As the Calumet and Hecla crews began dewatering the old Centennial No. 3 shaft, it became an important factor in the future of the area. In a nostalgic sense, it became a glance into history, a graphic illustration of how mining was carried on before the turn of the century…History lay buried beneath the water. As the water receded, the old workings told their story better than it could be told on the yellowing pages of some old mining record” (Courter, Ellis W., 1992, Michigan’s Copper Country. Contribution to Michigan Geology). The first five levels of the shaft were a reminder of the days when hand drilling was the norm. Evenly cut rock revealed the precision with which the miners worked. Below the fifth level was evidence of mechanization. “With drills operated by compressed air, the miners drilled deeper holes and accomplished their work faster. But the walls were more uneven and the drifts no longer appeared like carefully chiselled tunnels…The change in the drilling method was further evidenced by old pieces of drill steel. The hand held steel was short, not more than two feet long, with a chisel bit. The machine steel was longer with a cross bit” (Courter, Ellis W., 1992, Michigan’s Copper Country. Contribution to Michigan Geology). Considerable timbering had also been done in the old workings, as early mining methods did not include leaving pillars of supporting rock in the stopes. White Pine logs as large as three feet in diameter were discovered in spots, reminders of the magnificent forests that once thrived throughout the Keweenaw. After dewatering had been completed, exploratory drifts were driven northward from the 9th, 11th, and 17th levels, and from the bottom 31st level. Ore grade was found to increase in the lower levels of the mine, so with things looking good, a decision was made in 1964 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 to facilitate construction of the No. 6 shaft. 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 of 1972 Homestake Copper Company, a subsidiary of the well-known Homestake Mining Company, reached an agreement with Universal Oil Products (who had purchased Calumet and Hecla 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, Inc., and set about on a project (Nicknamed the "Key Project") to deepen the No. 6 shaft in hopes of intersecting the historically rich C&H Conglomerate, a native copper deposit that they hoped, with sufficient size, 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. At the same time, among other project goals, they hoped to construct a facility that could provide concentrating techniques and procedures.

The initial phase of the project began in April of 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 surface equipment at both the No. 3 and No. 6 shafts was renovated to support the mining operations.

Later that year, planning commenced on a pilot plant, and subsequently, a 750-ton-per-day concentrator was constructed near the No. 3 shaft and put into operation. Up to this point, ore had never been processed in modern conventional mills. The new milling process would grind the ore finer than the stamp mill methods of the past, allowing for better recovery. “The Key Project flow sheet included two stages of crushing, using a jaw crusher followed by a cone crusher. The jaw crusher product was conveyed to the cone crusher, where coarse copper was removed and the remaining product was crushed to minus ½ inch. This material was conveyed to a rod mill where mass copper was again removed. The rod mill discharge was pumped to a jig for further removal of mass copper. The jig tails were conveyed to a ball mill for grinding to minus 65 mesh and then transferred to the flotation circuits” (Dolbear, Behre, 2011). The mill operated on a 5-day schedule as mine production was limited.

In 1975, as the No. 6 shaft was nearing 6700 feet (Approx. 4150 vertical feet), it was reported that ore was also being mined in drifting operations out of the No. 3 shaft and brought to the surface to be processed in the new pilot plant. However, operations at both shafts would ultimately cease in the late ‘70s due to low copper prices and the completion of the exploration objectives. The objective of finding a native copper deposit that could support a larger operation did not come to fruition. Over the 18 months that the mill was in operation, “a total of 188,000 tons were mined and processed, and over 5 million pounds of copper were produced. Recoveries are estimated at greater than 90%” (Dolbear, Behre, 2011).

The mine would sit idle again, being allowed to fill with water, 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. It is unclear whether they planned to mine out of the No. 6 shaft alone, or both the No. 3 and No. 6 shafts, but news articles from the time suggest that they intended to utilize the mill near the No. 3 shaft. The Toronto-based company Great Lakes Minerals would end up purchasing 100% of Keweenaw Copper Company, who at the time owned 50% of 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 lb. of copper in concentrate” (The Northern Miner, 1990, Great Lakes boosts interest in Michigan copper projects). However, nothing came of this and operations ceased soon after. It is unknown whether any mining or milling activities took place at the No. 3 shaft during that time. Regardless, no activities have taken place since. 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, also noting that the mill had been dismantled.

The structures that remain at the site are privately owned and off limits to visitors, but can be viewed legally from Amygdaloid Street.

Other Regions, Features and Areas containing this locality

References