Taconite

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Taconite

Taconite is a ferrous , flint-like rock named for the Taconic Mountains in the United States . It is a Precambrian sedimentary rock that belongs to the band ores because of the typical alternation between iron-bearing layers and layers of slate or chert . The very finely distributed iron content in the form of magnetite is between 25 and 30%. The largest deposits in the world are in the Mesabi Range in Minnesota . In the late 19th and early 20th centuries, the available iron ore was of such high quality that taconite was viewed as an unprofitable waste product. However, after World War II , much of the high quality ore in the United States had already been mined, making taconite an economical new source of iron. To process taconite, the ore is ground to a fine powder, the iron is then separated from the rest of the rock with the help of strong magnets. The powdery iron concentrate is then rolled together with bentonite and lime as a flux into pellets about one centimeter in diameter, which consist of about 65% iron. The pellets are then heated to high temperatures for further processing in order to oxidize the magnetite (Fe 3 O 4 ) to hematite (Fe 2 O 3 ) .

The concentrated taconite is transported from the production facilities by rail to Silver Bay , Two Harbors and to the twin ports of Duluth and Superior on the Upper Lake , and then shipped by bulk carriers to other locations along the Great Lakes . Many steel-making factories are located near Lake Erie . Between 1900 and 1992 the ore was unloaded by large unloading machines, the so-called Hulett machines, which shaped the image of the region. Then self-unloading ships appeared and made these machines superfluous.

Harmfulness to health

The Minnesota State Department of Health has commissioned a study to determine whether the fibers or dust in taconite are associated with lung conditions such as pleural mesothelioma or asbestosis . A 2003 study of taconite miners found that the likely cause of 14 out of 17 cases of pleural mesothelioma was exposure to asbestos during taconite processing. In what is known as the Iron Range of Minnesota, pleural mesotheliomas are twice as common as the average.

Individual evidence

  1. ↑ Stephanie Hemphill: Researchers look for links between taconite and mesothelioma , Minnesota Public Radio. June 8, 2006. Retrieved July 18, 2007. 

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