Magnetite

Magnetite is a mineral whose primary component is an iron oxide that contains equal amounts of iron(II) and iron(III). Its empirical formula is Fe3O4, and it is often expressed as iron(II,III) oxide. In the past, it has been called ferrous–ferric oxide and triiron tetraoxide.

Magnetite's greatest use is as an important iron ore for steel manufacture. Other applications are as a catalyst in the Haber process for making ammonia, as a pigment for paints and ceramics, and as magnetic micro- and nanoparticles for a variety of processes and materials.

Magnetite is found in igneous, metamorphic, and sedimentary rocks. As its name implies, it is magnetic; it and other inherently magnetic iron-containing minerals are described as being ferrimagnetic. Magnetite is in the hexoctahedral crystal class; in the 3-D crystal structure, the purple atoms are iron, and the red atoms are oxygen.