The Caledonia Native Copper Mine

by Theodore J. Bornhorst and Richard C. Whiteman

Collection Tours of the Caledonia Mine

 

The Caledonia Mine, owned by Evergreen Explorations, is located near Mass, Michigan. The Caledonia Mine is southwest of the Mass and Adventure Mines within an area of native copper deposits outside of the major deposits of the Keweenaw Peninsula native copper district, some 40 km southwest of a major producer, the Baltic Mine.

The mines of the Mass area worked the Evergreen, Ogima, Butler, Mass, South Knowlton and Knowlton mineralized flow top lodes, termed the Evergreen Series, over a total strike length of about 5 km. The Evergreen Series produced about 33 million kg of copper at grades between 0.5 and 1.25 % (Weege and Pollack, 1971). The Mass Mine, largest producer in the area, produced 23 million kg of refined copper while the Adventure Mine produced 5 million kg from 1851 to 1923 (Butler and Burbank, 1929). The Butler Evergreen, and Knowlton lodes were the most productive of the flow tops; the Butler was the largest. The other flow tops yielded only small amounts of copper.

The Caledonia Mining Company commenced operations in 1863 after taking over lands of the Nebraska Company and adjacent Kansas Properties. The workings consisted of two shafts about 60 m (200 feet) deep and a 90 m (300 feet) long adit driven in the Butler lode on the west end of Caledonia bluff. Four adits were driven on a mineralized cross vein on the north side of the bluff, the only significant cross vein ever found in the Mass area. These four adits intersected the Knowlton, South Knowlton, Mass and Butler flow top lodes. Mining, mostly on the Knowlton and Butler, from 1863 until 1870 yielded about 410,000 kg of refined copper at a grade of about 1.25 % before fire destroyed the mill. The Caledonia Mine was combined with the Flintsteel properties in 1870 and a new mill was built to process accumulated ore. Only a small amount of mining was done before the operation was closed. In 1873 the Caledonia was leased by Captain Martin, who from 1873 to 1881 removed more than 150,000 kg of copper including a single mass weighing 36,000 kg (40 tons). An aborted plan was proposed in 1901 to reorganize the Caledonia properties to include all mineral lands between the Michigan and Adventure Properties with a mill site on Lake Superior.

The Caledonia Mine was dormant until 1937 when Calumet and Hecla Consolidated Copper Company, the major producer in the Keweenaw Peninsula native copper district, began a program of diamond drilling. This was followed by reopening of the No. 4 Caledonia adit with about 600 m (2000 feet) of drifting on the Knowlton lode. In addition, the adit was extended across the Evergreen Series to the Ogima lode, connecting with the Nebraska workings. Some drifting on the South Knowlton and Ogima lodes yielded poor results. Grade of ore from the Knowlton lode was estimated at 1.45 % copper. This project was stopped because of World War II.

In 1950 Calumet and Hecla Consolidated Copper Company removed a 200 ton bulk sample from the Knowlton lode with a grade of 1.84 % copper. Test mining and drifting commenced in 1951 and continued through 1958. This program included connecting the adit level to the Mass "C" shaft on the Knowlton lode, stoping on the Knowlton lode above the adit, drifting and stoping on the Butler and Evergreen lodes and limited diamond drilling. During this period 2.521 million kg of refined copper was produced at an average grade of 1.24 % copper.

Between 1971 and 1972 limited evaluation of the mine was done by Copper Range Company and the U.S. Bureau of Mines, including reopening the adit and inspecting the mine. Initially the Caledonia Mine was a candidate for insitu leaching but this idea was dropped due to potential problems of groundwater pollution.

Evergreen Exploration recently acquired the mine from Red Metal Exploration. The No. 4 Caledonia adit was reopened for a currently active program of exploration. The copper that is recovered is prepared and sold as specimens. The largest single piece removed to date weighed 1360 kg (3000 lbs). Other specimens recovered include native silver, datolite, calcite, epidote, adularia and native copper crystals.

REFERENCES
Bornhorst, T.J., An overview of the Keweenaw Peninsula native copper district, Michigan.
Broderick, T.M., 1931, Fissure vein and lode relations in Michigan copper deposits: Econ. Geol., v. 26, p. 840-856.
Butler, B.S., and Burbank, W.S., 1929, The copper deposits of Michigan: U.S. Geol. Survey Prof. Paper 144, 238p.
Calumet and Hecla, 1958, Unpublished report for Defense Minerals Exploration Administration, 29p.
Weege, R.J., and Pollack, J.O., 1971, Recent developments in native copper district of Michigan: Soc. of Economic Geologists Field Conference, Michigan Copper District, September 30 - October 2, 1971, p. 18-43.

Photographs: Top of page, copper from the Caledonia Mine, Right side of page, float copper in Calumet weighing 9,393 lbs.

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