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Octahedrites are the most common class of iron meteorite
Iron meteorite

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 man....
s. They are composed primarily of the nickel
Nickel

Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge....
-iron
Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
 alloy
Alloy

An alloy is a partial or complete solid solution of one or more chemical element in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history....
s: taenite
Taenite

Taenite is a mineral found naturally on Earth mostly in iron meteorites. It is an alloy of iron and nickel, with nickel proportions of 20% up to 65%....
 - high nickel content, and kamacite
Kamacite

Kamacite is a mineral. It is an alloy of iron and nickel, usually in the proportions of 90:10 to 95:5 although impurities such as cobalt or carbon may be present....
 - low nickel content.

Due to a long cooling time in the interior of the parent asteroid
Asteroid

Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, smaller than planets but larger than meteoroids....
s, these alloys have crystallized into intermixed millimeter-sized bands (from about 0.2 mm to 5 cm).






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Tolucameteorite
Octahedrites are the most common class of iron meteorite
Iron meteorite

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 man....
s. They are composed primarily of the nickel
Nickel

Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge....
-iron
Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
 alloy
Alloy

An alloy is a partial or complete solid solution of one or more chemical element in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history....
s: taenite
Taenite

Taenite is a mineral found naturally on Earth mostly in iron meteorites. It is an alloy of iron and nickel, with nickel proportions of 20% up to 65%....
 - high nickel content, and kamacite
Kamacite

Kamacite is a mineral. It is an alloy of iron and nickel, usually in the proportions of 90:10 to 95:5 although impurities such as cobalt or carbon may be present....
 - low nickel content.

Due to a long cooling time in the interior of the parent asteroid
Asteroid

Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, smaller than planets but larger than meteoroids....
s, these alloys have crystallized into intermixed millimeter-sized bands (from about 0.2 mm to 5 cm). When polished and acid etched the classic Widmanstätten pattern
Widmanstätten pattern

Widmanst?tten patterns, called also Thomson structures, are unique figures of long nickel-iron crystals, found in the octahedrite iron meteorites and some pallasites....
s of intersecting lines of lamellar kamacite, are visible.

In gaps between the kamacite and taenite lamellae, a fine-granied mixture called plessite
Plessite

Plessite is a fine-grained mixture of the minerals kamacite and taenite found in the octahedrite iron meteorites. It occurs in gaps between the larger bands of kamacite and taenite which form Widmanst?tten patterns....
 is often found. An iron nickel phosphide, schreibersite
Schreibersite

Schreibersite is a rare iron nickel phosphide mineral, 3P, found in iron-nickel meteorites. Another name used for the mineral is rhabdite....
, is present in some nickel-iron meteorites as well as an iron nickel cobalt
Cobalt

Cobalt is a hard, lustrous, grey metal, a chemical element with symbol Co and atomic number 27. Although cobalt-based colors and pigments have been used since ancient times, and miners have long used the name kobold ore for some minerals, cobalt was only discovered in 1735 by Georg Brandt....
 carbide
Carbide

In chemistry, a carbide is a compound composed of carbon and a less electronegativity element. Carbides can be generally classified by chemical bonding type as follows: salt-like, covalent compounds, interstitial compounds, and "intermediate" transition metal carbides....
, cohenite.

Chemical classification

Concentrations of trace elements are used to separate the iron meteorite
Iron meteorite

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 man....
s into chemical classes, which correspond to separate asteroid
Asteroid

Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, smaller than planets but larger than meteoroids....
 parent bodies:
  • IAB iron meteorites
  • IC iron meteorites
  • IIAB iron meteorites (includes also some hexahedrite
    Hexahedrite

    Hexahedrites are a type of iron meteorite.They are composed almost exclusively of the nickel-iron alloy kamacite, and are lower in nickel content than the Octahedrites....
    s)
  • IIC iron meteorites
  • IID iron meteorites
  • IIE iron meteorite
    IIE iron meteorite

    The iron meteorites of the IIE chemical type are octahedrites of various coarseness, most of which contain numerous inclusion s of recrystallization stony silicates....
    s
  • IIG iron meteorites (includes also some hexahedrite
    Hexahedrite

    Hexahedrites are a type of iron meteorite.They are composed almost exclusively of the nickel-iron alloy kamacite, and are lower in nickel content than the Octahedrites....
    s)
  • IIF iron meteorites (includes also some ataxite
    Ataxite

    Ataxites are a class of iron meteorites. They are composed mainly of the alloy taenite, and also contain plessite, troilite, and microscopic lamellae of kamacite....
    s)
  • IIIAB iron meteorites
  • IIICD iron meteorites
  • IIIE iron meteorites
  • IIIF iron meteorites
  • IVA iron meteorites
For a full list see iron meteorite
Iron meteorite

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 man....
s

Mineral

Octahedrite is also an obsolete synonym for anatase
Anatase

Anatase is one of the three mineral forms of titanium dioxide, the other two being brookite and rutile. It is always found as small, isolated and sharply developed crystals, and like rutile, a more commonly occurring modification of titanium dioxide, it crystallizes in the Tetragonal crystal system; but, although the degree of symmetry is...
, one of the three known titanium
Titanium

Titanium is a chemical element with the symbol Ti and atomic number 22. Sometimes called the ?space age metal?, it has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver colour....
 dioxide mineral
Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
s.