What is the compound Fe3O4?

Fe3O4 is actually a combination of two separate compounds, Fe2O3 and FeO. Fe203 is more commonly known as ferric oxide, and FeO is otherwise known as ferrous oxide. Fe3O4 is also known as magnetite or lodestone in mineral form.

The current accepted scientific name for Fe3O4 is Iron(II,III) oxide. Its most common use is as a black pigment. Fe3O4's attraction as a black pigment is because it can be synthesised rather than extracted from the naturally occurring minerals. This is made more useful as the particle size and shape can be varied by the methods used in the production of Fe3O4.