Iron oxide

Iron oxide

Overview

Iron oxides are chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

s composed of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

. All together, there are sixteen known iron oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....

s and oxyhydroxides.

Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g., as iron ores, pigments, catalysts, in thermite
Thermite
Thermite is a pyrotechnic composition of a metal powder and a metal oxide that produces an exothermic oxidation-reduction reaction known as a thermite reaction. If aluminium is the reducing agent it is called an aluminothermic reaction...

 (see the diagram).
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Encyclopedia

Iron oxides are chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

s composed of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

. All together, there are sixteen known iron oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....

s and oxyhydroxides.

Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g., as iron ores, pigments, catalysts, in thermite
Thermite
Thermite is a pyrotechnic composition of a metal powder and a metal oxide that produces an exothermic oxidation-reduction reaction known as a thermite reaction. If aluminium is the reducing agent it is called an aluminothermic reaction...

 (see the diagram). Common rust
Rust
Rust is a general term for a series of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture...

 is a form of iron(III) oxide.

Oxides

  • iron(II) oxide
    Iron(II) oxide
    Iron oxide, also known as ferrous oxide, is one of the iron oxides. It is a black-colored powder with the chemical formula . It consists of the chemical element iron in the oxidation state of 2 bonded to oxygen. Its mineral form is known as wüstite. Iron oxide should not be confused with rust,...

    , wüstite
    Wüstite
    Wüstite is a mineral form of iron oxide found with meteorites and native iron. It has a gray color with a greenish tint in reflected light. Wüstite crystallizes in the isometric - hexoctahedral crystal system in opaque to translucent metallic grains. It has a Mohs hardness of 5 to 5.5 and a...

     (FeO)
  • iron(II,III) oxide
    Iron(II,III) oxide
    Iron oxide is the chemical compound with formula Fe3O4. It is one of a number of iron oxides, the others being iron oxide , which is rare, and iron oxide also known as hematite. It occurs in nature as the mineral magnetite. It contains both Fe2+ and Fe3+ ions and is sometimes formulated as FeO ∙...

    , magnetite
    Magnetite
    Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...

     (Fe3O4)
  • iron(III) oxide
    Iron(III) oxide
    Iron oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron oxide , which is rare, and iron oxide , which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe2O3 is the main...

     (Fe2O3)
    • alpha phase, hematite
      Hematite
      Hematite, also spelled as haematite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...

       (α-Fe2O3)
    • beta phase, (β-Fe2O3)
    • gamma phase, maghemite
      Maghemite
      Maghemite is a member of the family of iron oxides. It has the same structure as magnetite, that is, it is spinel ferrite and is also ferrimagnetic.Maghemite can be considered as an Fe-deficient magnetite with formula...

       (γ-Fe2O3)
    • epsilon phase, (ε-Fe2O3)

Hydroxides

  • iron(II) hydroxide
    Iron(II) hydroxide
    Iron hydroxide or ferrous hydroxide is a compound produced when iron ions, from a compound such as iron sulfate, react with hydroxide ions. Iron hydroxide itself is practically white, but even traces of oxygen impart it with a greenish tinge...

     (Fe(OH)2)
  • iron(III) hydroxide (Fe(OH)3), (bernalite)

Oxide/hydroxides


  • goethite
    Goethite
    Goethite , named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment samples...

     (α-FeOOH),
  • akaganéite
    Akaganéite
    Akaganéite is an iron oxide-hydroxide / chloride mineral with formula: Fe3+O e.g; β-FeO. It is formed by the weathering of pyrrhotite . Nickel also has been reported in the structure. It has a monoclinic crystal structure, a metallic luster and a brownish yellow streak. It is named after the...

     (β-FeOOH),
  • lepidocrocite
    Lepidocrocite
    Lepidocrocite , also called esmeraldite or hydrohematite, is an iron oxide-hydroxide mineral. Lepidocrocite has an orthorhombic crystal structure, a hardness of 5, specific gravity of 4, a submetallic luster and a yellow-brown streak. It is red to reddish brown and forms when iron-containing...

     (γ-FeOOH),
  • feroxyhyte
    Feroxyhyte
    Feroxyhyte is an oxide/hydroxide of iron, δ-Fe3+O. Feroxyhyte crystallizes in the hexagonal system. It forms as brown rounded to concretionary masses. Feroxyhyte is opaque, magnetic, has a yellow streak, and has a relative density of 4.2....

     (δ-FeOOH),
  • ferrihydrite
    Ferrihydrite
    Ferrihydrite is a widespread hydrous ferric oxyhydroxide mineral at the Earth's surface, and a likely constituent in extraterrestrial materials. It forms in several types of environments, from freshwater to marine systems, aquifers to hydrothermal hot springs and scales, soils, and areas affected...

     (Fe5HO8·4H2O approx.), or 5Fe2O3•9H2O, better recast as FeOOH•0.4H2O

  • high-pressure FeOOH
  • schwertmannite
    Schwertmannite
    Schwertmannite is an iron-oxyhydroxysulfate mineral with an ideal chemical formula of 886·nH2Oor Fe3+16O1612-13·10-12H2O. It is an opaque tetragonal mineral typically occurring as brownish yellow encrustations...

     (ideally Fe8O8(OH)6(SO)·nH2O or Fe3+16O16(OH,SO4)12-13·10-12H2O)
  • green rusts (FeIIIxFeIIy(OH)3x+2y-z(A-)z; where A- is Cl- or 0.5SO42-)

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