Pure iron tetroxide is a black solid. Because of its special crystal structure and the characteristics of Fe element as transition metal, it is magnetic. Fe3O4 is a complex ionic crystal composed of Fe2 +, Fe3 +, O2 + through ionic bond. The arrangement of ions is similar to spinel structure. Fe3O4 belongs to the anti spinel configuration. Because of the alternating arrangement of Fe2 + and Fe3 + in the crystal, electrons are easily transferred from Fe2 + to Fe3 + due to the influence of electric field, so Fe3O4 has high conductivity.