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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 ...
Some examples of minerals in iron-rich rocks containing oxides are limonite, hematite, and magnetite. An example of a mineral in iron-rich rock containing carbonates is siderite and an example of minerals in an iron-rich rock containing silicate is chamosite. [2] They are often interbedded with limestones, shales, and fine-grained sandstones.
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]
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. Ore typically contains around 8% to 12% water, and <5% SiO 2, and <3% Al 2 O 3. The hydrous iron oxides can be calcined, and the CID ore on a volatile-free basis is around 63% Fe or more.
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).
The term can also refer to the process by which waterborne minerals, such as calcium carbonate , iron oxide (hematite or limonite) or silica , replace organic material within the body of an organism that has died and was buried by sediments. [2] Mineralization may also refer to the product resulting from the process of mineralization.
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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.