The Mining of Taconite, Lake Superior Iron Mining District

T I lHE exploitation of taconite, a hard sedimentary rock containing 20 to 35 per cent iron, has had a rejuvenating effect on mining in the Lake Superior Iron Mining District of northern Minnesota, Wisconsin, and Michigan. This development comes at a time when the shipment of highgrade ores obtained by open-pit and shaft mining has passed its peak. Taconite is presently being mined in two of the six ranges of the Lake Superior District, the Mesabi and the Marquette (Fig. 1). Plans have also been announced for the establishment of a concentration plant on the Menominee Range some fifteen miles northeast of Iron Mountain, Mich., and it is expected that a pelletizing plant for low-grade iron ore will be in operation by 1960 on the Gogebic Range in the Town of Agenda, northern Wisconsin. The exploitation of taconite-or, in Michigan, jasper-requires the investment of enormous amounts of capital, but it is estimated that the reserves of taconite in Minnesota alone will yield more than two billion tons of iron concentrates, an amount equivalent to the total tonnage of ore shipped from the Mesabi Range between 1892 and 1954. Legally, taconite is a ferruginous chert or slate in the form of a compact siliceous rock, in which the iron oxide is so finely disseminated that substantially all the iron-bearing particles of merchantable grade ore are smaller than 20 mesh.' In Minnesota taconite is obtained from the Biwabik iron formation that underlies the Mesabi outcrop for about a hundred miles between Babbitt and Grand Rapids, in northern Minnesota. The formation is some 400 to 750 feet thick and ranges in width from half a mile to two miles and a half Hematite, the ore that made the name Mesabi famous, was originally taconite. Over the course of time, water leached much of the silica from some of the taconite deposits, leaving large areas of relatively pure iron oxide. Until now, the steel industry in the United States has been based chiefly on the utilization of these high-grade ores. In recent years, however, many hematite mines have passed their peak of production, and the Lake Superior

Archaeology · Geography · Mining engineering · Clay minerals and soil interactions · Environmental Science · Geology · Minerals Flotation and Separation Techniques

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