page_title: Banded iron formation
section_title: Economic geology
hierarchical_section_title: Banded iron formation / Economic geology
caption_attribution_description: English: Iron Ore mine at Tom Price, Western AustraliaDeutsch: Eisenerztagebau nahe Tom Price (West Australien)
context_page_description: Banded iron formations are distinctive units of sedimentary rock consisting of alternating layers of iron oxides and iron-poor chert. Almost all of these formations are of Precambrian age and are thought to record the oxygenation of the Earth's oceans.
  A typical banded iron formation consists of repeated, thin layers of silver to black iron oxides, either magnetite or hematite, alternating with bands of iron-poor chert, often red in color, of similar thickness. A single banded iron formation can be up to several hundred meters in thickness and extend laterally for several hundred kilometers.
  Banded iron formations are thought to have formed in sea water as the result of oxygen production by photosynthetic cyanobacteria. The oxygen combined with dissolved iron in Earth's oceans to form insoluble iron oxides, which precipitated out, forming a thin layer on the ocean floor. Each band is similar to a varve, resulting from cyclic variations in oxygen production.
  Some of the Earth's oldest rock formations, which formed about 3,700 million years ago, are associated with banded iron formations.
context_section_description: Banded iron formations provide most of the iron ore presently mined and thus are fundamental to the prosperity of the industrialized world. More than 60% of global iron reserves are in the form of banded iron formation, which can be found in Australia, Brazil, Canada, India, Russia, South Africa, Ukraine, and the United States.
  Different mining districts coined their own names for BIFs. The term "banded iron formation" was coined in the iron districts of Lake Superior, where the ore deposits of the Mesabi, Marquette, Cuyuna, Gogebic, and Menominee iron ranges were also variously known as "jasper", "jaspilite", "iron-bearing formation", or taconite. Banded iron formations were described as "itabarite" in Brazil, as "ironstone" in South Africa, and as "BHQ" (banded hematite quartzite) in India.
  Banded iron formation was first discovered in northern Michigan in 1844, and mining of these deposits prompted the earliest studies of banded iron formation, such as those of Van Hise and Leith. Iron mining operations on the Mesabi and Cuyuna Ranges evolved into enormous open pit mines, where steam shovels and other industrial machines could remove massive amounts of ore. Initially the mines exploited large beds of hematite and goethite weathered out of the banded iron formations, and some 2.5 billion tons of this "natural ore" had been extracted by 1980. By 1956 large-scale commercial production from the BIF itself began at the Peter Mitchell Mine near Babbitt, Minnesota. Production in Minnesota was 40 million tons of ore concentrate per year in 2016, which is about 75% of total U.S. production. Magnetite-rich banded iron formation, known locally as taconite, is ground to a powder, and the magnetite is separated with powerful magnets and pelletized for shipment and smelting.
  Iron ore became a global commodity after the Second World War, and with the end of the embargo against exporting iron ore from Australia in 1960, the Hamersley Range became a major mining district. The banded iron formations here are the thickest and most extensive in the world, originally covering an area of 150,000 square kilometers (58,000 square miles) and containing about 300 trillion metric tons of iron. The range contains 80 percent of all identified iron ore reserves in Australia. Over 100 million metric tons of iron ore is removed from the range every year.
  The Itabarite banded iron formations of Brazil cover at least 80,000 square kilometers (31,000 square miles) and are up to 600 meters (2,000 feet) thick. These form the Quadrilatero Ferrifero or Iron Quadrangle, which resembles the Iron Range mines of United States in that the best ore is hematite weathered out of the BIFs. Production from the Iron Quadrangle helps make Brazil the second largest producer of iron ore, with monthly exports averaging 139,299 metric tons from December 2007 to May 2018.
  Mining of ore from banded iron formations at Anshan in north China began in 1918. When Japan occupied Northeast China in 1931, these mills were turned into a Japanese-owned monopoly, and the city became a significant strategic industrial hub during World War II. Total production of processed iron in Manchuria reached 1,000,000 metric tons in 1931–32. By 1942, Anshan's Shōwa Steel Works total production capacity reached 3,600,000 metric tons per annum, making it one of the major iron and steel centers in the world. Production was severely disrupted during the Soviet occupation of Manchuria in 1945 and the subsequent Chinese Civil War. However, from 1948 to 2001, the steel works produced 290 million tons of steel, 284 million tons of pig iron and 192 million tons of rolled steel. Current annual production capacity is 10 million tons of pig iron, 10 million tons of steel and 9.5 million tons of rolled steel. A quarter of China's total iron ore reserves, about 10 billion tons, are located in Anshan.
caption: Tom Price Mine, Hamersley Range, Australia
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