Iron oxide

Iron oxides are chemical compounds.  They are made of iron and oxygen. There are sixteen known iron oxides. Iron oxides are used in pigments. It is used in both man-made and natural pigments. Iron oxides are often non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust.

Iron oxides and oxyhydroxides are widespread in nature and play an important role in many geological and biological processes.  They are used as iron ores, pigments, catalysts, and in thermite, and occur in hemoglobin. Iron oxides are inexpensive and durable pigments in paints, coatings and colored concretes. Colors commonly available are in the "earthy" end of the yellow/orange/red/brown/black range. When used as a food coloring, it has E number E172.

Venetian red (haematite), Magnetite (Fe3O4), or a mixture of oxides make black or purple pigments. The umber, sienna and ochre are oxides or hydrated oxides of a yellow to chestnut colour.

Most iron oxide is mined as iron ore. Every year millions of tons go into blast furnaces to make iron.  

 Various iron oxides 

Iron(III) oxide, reddish, commonly known as rust, found in the earth as haematite
Iron(II,III) oxide, magnetic, black, found in the earth as magnetite
Iron(II) oxide, black, rare, flammable, not stable at room temperature
Iron(II) hydroxide, dark green hydrated iron oxide

List of pigments (or iron oxide pigments)
Caput mortuum (pigment)
Earth pigment
Falu red
Ferrihydrite
Goethite
Golden ochre
Hematite
Hemosiderin

Iron oxide
Iron oxide red
Iron(II,III) oxide
Iron(II) oxide
Iron(III) oxide
Magnetite
Mars Black (pigment)
Mummy brown
Ochre and Attic ochre
Red Ochre

Sienna
Sinopia

Umber

Venetian red

 References 

Category:Iron compounds
Category:Oxides
Category:Inorganic pigments

de:Eisen#Oxide