Iron ore is the most important mineral to Minnesota’s economy, accounting for 83 percent of the state’s nonfuel mineral production value in 1997. Minnesota has been the leading producer of iron ore in the United States almost since the opening of its iron ranges in the northeastern part of the state in the 1880s. One of the three major iron ranges was the Vermilion Range, which produced ore until the mid-1960s. Most of its mines were located in the Ely-Winton and Tower-Soudan areas. Later, the Mesabi Range became the most productive range. Its numerous mines extend almost continuously for a distance of more than 130 km (80 mi). In this range, near Hibbing, the Hull-Rust group of mines began production in the 1890s and until the mid-1980s was the world’s largest open-pit mine. The third important range was the Cuyuna Range, near Crosby and Ironton. Until the late 1960s this range was a producer of ore containing manganese as well as iron. Ore from Minnesota’s mines is shipped by rail to ports on Lake Superior, where it is loaded onto special ships for transport to steel mills.
Over the years the accessible high-grade iron ore reserves have been nearly used up, and most of the underground mines and many of the open-pit mines in northeastern Minnesota have had to close down. However, Minnesota has an abundance of flintlike rock known as taconite and semitaconite. When it became apparent that the high-grade ore reserves would soon be exhausted, Edward W. Davis of the University of Minnesota Mines Experiment Station began working on a process to remove the iron minerals, such as hematite and magnetite, contained in taconite.
In the late 1940s, after decades of unsuccessful experimentation, Davis devised a method for grinding the hard taconite rock, removing the magnetic particles of the iron minerals, and recementing these particles into pellets usable in blast furnaces. The uniformity of these pellets has made them a desirable substitute for high-grade iron ores.
At the eastern end of the Mesabi Range there are huge reserves of magnetic taconite, which should enable the state to remain the nation’s leading iron ore producer for many years to come. Today almost all of the iron ore produced in Minnesota is taconite. Sand, gravel, and stone are other leading mineral products. Sand and gravel are produced throughout the state. Most of the stone output consists of crushed limestone, dolomite, and granite. Other minerals produced in Minnesota are lime, clay, peat, and abrasive stone, which is mined near Jasper. "Minnesota" © Emmanuel BUCHOT, Encarta, Wikipedia
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