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Metallic iron is virtually unknown 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 the Earth's crust, composing about 5%, the vast majority is bound in silicate or, more rarely, carbonate minerals, and smelting pure iron from these minerals would require a prohibitive amount of ...
As such, iron is the most abundant element in the core of red giants, and is the most abundant metal in iron meteorites and in the dense metal cores of planets such as Earth. [29] It is also very common in the universe, relative to other stable metals of approximately the same atomic weight.
Iron meteorites consist overwhelmingly of nickel-iron alloys. The metal taken from these meteorites is known as meteoric iron and was one of the earliest sources of usable iron available to humans. Iron was extracted from iron–nickel alloys, which comprise about 6% of all meteorites that fall on the Earth.
When a metallic ore is an ionic compound, the ore must usually be smelted—heated with a reducing agent—to extract the pure metal. Many common metals, such as iron, are smelted using carbon as a reducing agent. Some metals, such as aluminum and sodium, have no commercially practical reducing agent, and are extracted using electrolysis instead.
Roughly 5 grams of iron are present in the human body and is the most abundant trace metal. [1] It is absorbed in the intestine as heme or non-heme iron depending on the food source. Heme iron is derived from the digestion of hemoproteins in meat. [4] Non-heme iron is mainly derived from plants and exist as iron(II) or iron(III) ions. [4]
Iron formations can be divided into subdivisions known as: banded iron formations (BIFs) and granular iron formations (GIFs). [ 3 ] The above classification scheme is the most commonly used and accepted, though sometimes an older system is used which divides iron-rich sedimentary rocks into three categories: bog iron deposits , ironstones , and ...
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Iron supply is an important factor affecting growth of phytoplankton, the base of marine food web. [27] Offshore regions rely on atmospheric dust deposition and upwelling. [21] Other major sources of iron to the ocean include glacial particulates, hydrothermal vents, and volcanic ash. [28]