A jumbo is a mobile drill carriage or scaffold on which several drills could be mounted. The Cliffs Shaft Mine in Ishpeming in the Marquette Range was the largest producer of hard specular hematite in the US. The Cliffs Shaft Mine (New Barnum Mine) was opened by the Iron Cliffs Company in 1881 and operated by the Cleveland-Cliffs Iron Company starting in 1891. The Mine was one of Michigan's largest iron mines and operated almost continuously until its closure in 1967. Cleveland-Cliffs Iron Company was formed with the merger of two major iron mining companies on Michigan's Marquette Range in 1891. The Company had a number of mines operating in the Upper Peninsula by the outbreak of World War I. By the 1940s the high grade iron ores mined underground were becoming depleted. The Company developed a process to concentrate low grade ores into iron ore pellets in the 1950s, and C.C.I.C.'s last underground iron mine closed in 1979.
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