Abstract The Caledonia Mine, owned by Red Metal Explorations, is located near Mass, Michigan (Fig. 1). The Caledonia Mine is southwest of the Mass and Adventure Mines (Fig. 2) 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 (see Fig. 3 of Bornhorst, this volume). 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 Cu 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.