Iron oxide

[1] Iron oxides and oxyhydroxides are widespread in nature and play an important role in many geological and biological processes.

Iron oxides are inexpensive and durable pigments in paints, coatings and colored concretes.

Only a few oxides are significant at the earth's surface, particularly wüstite, magnetite, and hematite.

In blast furnaces and related factories, iron oxides are converted to the metal.

Iron oxides are important pigments, coming in a variety of colors (black, red, yellow).

Electrochemically oxidized iron (rust)
Iron oxide pigment. The brown color indicates that iron is at the oxidation state +3.
Green and reddish brown stains on a limestone core sample, respectively corresponding to oxides/hydroxides of Fe 2+ and Fe 3+ .