Taconite

Source: Wikipedia, the free encyclopedia.
For the city in the United States, see Taconite, Minnesota.
Taconite
Sedimentary iron formation rock
Composition
PrimaryMagnetite, hematite and chert
SecondarySiderite, greenalite, minnesotaite and stilpnomelane

Taconite (/ˈtækənaɪt/) is a variety of banded iron formation, an iron-bearing (over 15% iron) sedimentary rock, in which the iron minerals are interlayered with quartz, chert, or carbonate. The name "taconyte" was coined by Horace Vaughn Winchell (1865–1923) – son of Newton Horace Winchell, the Minnesota State Geologist – during their pioneering investigations of the Precambrian Biwabik Iron Formation of northeastern Minnesota. He believed the sedimentary rock sequence hosting the iron-formation was correlative with the Taconic orogeny of New England, and referred to the unfamiliar and as-yet-unnamed iron-bearing rock as the 'taconic rock' or taconyte.[1]

Following development of high grade direct shipping

silica
, miners termed the unaltered iron-formation wall rock taconite. The iron content of taconite is generally 30% to 35%, and the silica content generally around 45%. Iron in taconite is commonly present as magnetite, iron silicates, and iron-bearing carbonates, and locally martite (hematite) formed by oxidation of magnetite. Horizons containing magnetite as the dominant mineral have been extensively mined since 1955 to produce iron ore pellets; the term 'taconite' has consequently been colloquially adapted to describe the magnetite iron-formation ores (taconite iron ore), the mining, milling, magnetic separation, and agglomerating process (taconite process), and the product iron ore pellets (taconite pellets).

History

In the late 19th and early 20th centuries, the United States was mining such an abundance of iron ore of high quality that taconite was considered an uneconomic waste product. By the end of World War II much of the high-grade iron ore in the United States had been exhausted, so taconite became valued as a new source of the metal.[2]

Production

To process taconite, the ore is ground into a fine powder, the magnetite is separated from the

exothermic reaction that reduces the cost of pelletizing the concentrate. E. W. Davis of the University of Minnesota Mines Experiment Station is credited with developing the pelletizing process. Since the commercial development of this process in the Lake Superior region in the 1950s, the term "taconite" has been used globally to refer to iron ores amenable to upgrading by similar processes.[citation needed
]

Major producers of iron ore pellets from taconite in North America include

Cliffs Natural Resources, Inc., U.S. Steel, and ArcelorMittal. These processed taconite-ore pellets are also referred to as "taconite". Because this is the form that is typically transported by rail and ship, and cargo of these is often discussed, this usage of the term is very common.[citation needed
]

Processed taconite pellets as used in the steelmaking industry, with a US quarter shown for scale.

The

Twin Ports of Duluth, Minnesota, and Superior, Wisconsin, all on Lake Superior. The docks at Escanaba, Michigan, on Lake Michigan, also ship taconite from the Marquette iron range in Michigan, and occasionally ore from Minnesota is hauled by rail there. Marquette, Michigan, also has a taconite dock that loads bulk freighters with ore from the Marquette iron range. The ore is generally shipped by lake freighters to locations on the lower Great Lakes. Many steelmaking centers are near Lake Erie. Due to increased international demand, taconite is shipped to Mexico and China.[3]

The SS

long tons of taconite pellets.[4]

Taconite and human health

Beginning in 1955, Reserve Mining Company discharged crushed waste rock (tailings) from their Silver Bay, Minnesota processing plant into Lake Superior. The tailings contained 40% of the amphibole group mineral series cummingtonite-grunerite, which may form asbestiform particles. A small fraction of the fine-grained tailings were shown to widely disperse along the western shore of Lake Superior, the source of drinking water for a number of cities; for example, tests of Duluth, Minnesota's water supply showed 100 billion fibers per liter of water. There was no epidemiological proof whether these particles caused cancer or were safe. On April 20, 1974, the U.S. District Court judge Miles Lord ruled that the drinking water and Lake Superior must be protected from the asbestos-like particles. The Reserve Mine was forced to begin disposing of tailing wastes on the land, and to implement air pollution control equipment, instead of discharging them directly to Lake Superior. This became one of the costliest pollution prevention cases in U.S. history.[5] Government-funded studies have found no adverse health effects from drinking Lake Superior water.[6][7]

A 2003 study of taconite miners concluded that the most likely cause of 14 of the 17 cases of

pleural conditions which occur following asbestos exposure. Because these conditions can be triggered by industrial asbestos, which was used in taconite mining and processing, as well as other industrial facilities in northeastern Minnesota, the study attempted to determine what, if any, influence naturally occurring fibrous minerals in taconite may have played.[8] The lengthy epidemiological study of Minnesota iron miners concluded in December 2014 that those working 30 years in the iron mines and living to be 80 years old had a lifetime chance of having a mesothelioma of 3.33 cases per thousand such workers, more than double the background rate of 1.44 cases per thousand people living to 80 years old.[9]

See also

  • Edward Wilson Davis – American engineer and inventor pioneering early research in taconite
  • Banded iron formation – Distinctive layered units of iron-rich sedimentary rock that are almost always of Precambrian age

References

  1. ^ Winchell, Horace V. (1891) "The Mesabi iron range," in: Winchell, Newton H., ed., The Geological and Natural History Survey of Minnesota (Minneapolis, Minnesota, USA: Harrison & Smith), vol. 20, p. 124. From p. 124: "This rock is widely spread over the whole length of the Mesabi, and being different from anything found elsewhere and peculiar to this horizon of the Taconic, has been called taconyte by the writer."
  2. ^ "Taconite". Minnesota Department of Natural Resources. Retrieved 27 December 2023.
  3. ^ [1], Future Work
  4. ^ National Transportation Safety Board (NTSB) (May 4, 1978). "Marine Accident Report: SS Edmund Fitzgerald Sinking in Lake Superior on November 10, 1975" (PDF). uscg.mil. NTSB. p. 9. Archived (PDF) from the original on 2017-05-02. Retrieved 2017-03-29.
  5. ^ Thomas R. Huffman, "Enemies of the People, Asbestos and the Reserve Mining Trial"
  6. ^ E. E. Sigurson, "Observations of cancer incidence surveillance in Duluth, Minnesota," Environmental Health Perspectives, Nov. 1983, v.53 p61-67.
  7. ^ Hilding and others, "Biological effects of ingested amosite asbestos, taconite tailings, diatomaceous earth and Lake Superior water in rats," Archives of Environmental Health, Nov.-Dec. 1981, v.36 n.6 p.298-303.
  8. ^ a b Hemphill, Stephanie (2007-06-08). "Researchers look for links between taconite and mesothelioma". Minnesota Public Radio. Retrieved 2007-07-18.
  9. ^ Finnegan, John R. Jr; Mandel, Jeffery H. (24 November 2014). Final Report to the Legislature: Minnesota Taconite Worker's Health Study (PDF) (Report). Minnesota Taconite Workers Lung Health Partnership. p. 23.

Further reading

  • Davis, Edward W., Pioneering With Taconite. St. Paul: Minnesota Historical Society Press, 1964.
  • Erie Mining Company History Project Team, Taconite, New Life for Minnesota's Iron Range: The History of Erie Mining Company. Duluth: St. Louis County Historical Society, 2019.
  • Manuel, Jeffrey T., "Mr. Taconite: Edward W. Davis and the Promotion of Low-Grade Iron Ore, 1913–1955," Technology and Culture, 54 (April 2013), 317–45.
  • Manuel, Jeffrey T., Taconite Dreams: The Struggle to Sustain Mining on Minnesota's Iron Range, 1915-2000. Minneapolis: University of Minnesota Press, 2015.

External links

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