fə]|rōsə, fe]+...- noun
Etymology: International Scientific Vocabulary ferroso- + ferric
: a black magnetic iron oxide Fe 3 O 4 found in nature as magnetite, also obtained synthetically (as from iron by heating in steam or from a ferrous salt and an alkali by precipitation and oxidation), and used chiefly as a pigment and polishing material — called also iron(II,III) oxide