Fe2O3

Iron(III) oxide, Fe2O3, is an inorganic compound that occurs naturally as the mineral hematite. It is one of the most common oxides of iron and an important iron ore. Hematite is typically reddish to reddish-brown in color and can be found in massive, tabular, or powdery forms. It is the most thermodynamically stable oxide of iron under ordinary conditions.

Hematite forms through the oxidation of iron-bearing minerals, precipitation from iron-rich waters, or as a weathering product of magnetite and other iron minerals. It is mined on a large scale as a source of iron for steel production. Hydrated forms such as goethite can dehydrate to hematite when heated.

Chemically, Fe2O3 has a molar mass of 159.69 g/mol and a density of about 5.24–5.26 g/cm³. It is insoluble in water and only slightly soluble in acids. The compound is heat-stable, with a high melting point. In terms of magnetism, hematite is weakly ferromagnetic at room temperature due to spin canting in an antiferromagnetic lattice; below a Morin transition around 260 K, it adopts a strictly antiferromagnetic arrangement.

Crystal structure is the corundum-type, derived from the hexagonal close-packed oxide lattice, with iron ions occupying octahedral sites in an Fe2O3 framework.

Applications include use as a pigment (red ochre), a major iron ore for steelmaking, and, in nanomaterial form, as a basis for catalysts and certain magnetic applications. Hematite can be produced by heating goethite or by oxidation of iron salts, among other methods.