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Elemental iron is virtually absent on the Earth's surface except as iron-nickel alloys from meteorites and very rare forms of deep mantle xenoliths.Although iron is the fourth most abundant element in Earth's crust, composing about 5% by weight, [4] the vast majority is bound in silicate or, more rarely, carbonate minerals, and smelting pure iron from these minerals would require a prohibitive ...
Iron plays an important role in the nitrogen cycle, aside from its role as part of the enzymes involved in nitrogen fixation. In anoxic conditions, Fe(II) can donate an electron that is accepted by NO 3 − which is oxidized to several different forms of nitrogen compounds, NO 2 − , N 2 O, N 2 , and NH 4 + , while Fe(II) is reduced to Fe(III).
Hematite and magnetite are the most common types of Iron ore. Roughly 98% of iron ore on the global market is used in iron and steel production. [8] The other 2% of iron ore is used to make powdered iron for certain types of steel, auto parts, and catalysts; radioactive iron for medicine; and iron blue in paints, inks, cosmetics, and plastics. [5]
Economically important iron deposits include: Carajás Mine in the state of Pará, Brazil, is thought to be the largest iron deposit in the world. El Mutún in Bolivia, where 10% of the world's accessible iron ore is located. Hamersley Basin is the largest iron ore deposit in Australia.
Channel iron deposits are an important source of iron ore, with the deposits at Yandi and Robe River accounting for approximately 47% of iron ore mined from the Hamerley Iron province. Although channel iron deposits are typically low-grade at 53% to 57% Fe in-situ, they are composed of goethite-limonite which are hydrated iron oxide species.
The geology of the Kiruna ore has many parallels to that of the iron ore of El Laco volcano in Chile, leading to the claim they were both formed by volcanic activity. [20] In 1973 Tibor Parák pointed out a series of problems with the magmatic origin theory and proposed instead that the ore originated as a sediment in a volcanic environment. [21]
Ocean iron fertilization is an example of a geoengineering technique that involves intentional introduction of iron-rich deposits into oceans, and is aimed to enhance biological productivity of organisms in ocean waters in order to increase carbon dioxide (CO 2) uptake from the atmosphere, possibly resulting in mitigating its global warming effects.
While the first iron ore was likely meteoric iron, and hematite was far easier to smelt, in Africa, where the first evidence of iron metallurgy occurs, [dubious – discuss] limonite is the most prevalent iron ore. Before smelting, as the ore was heated and the water driven off, more and more of the limonite was converted to hematite.