Sesquióxido

A sesquioxide is an oxide containing three oxygen atoms with two atoms (or radicals) of another element, for example aluminum oxide (Al2O3) is a sesquioxide. Many sesquioxides contain the metal in the 3+ oxidation state, such as Al 2 O 3, Fe 2 O 3 or La 2 O 3, however the alkali metal sesquioxides are exceptions and contain both peroxide (O2) and superoxide (O2) ions, eg Rb2O3 is formulated [ Rb) 4 (O 2) (O 2) 2].

Iron and aluminum sesquioxides are largely found in soil.

wiki