MnO2 – manganese(IV) oxide – is a dark brown powder, insoluble in water. It is the most stable compound of manganese, and is widespread in the earth's crust as a mineral known as pyrolusite. Manganese(IV) oxide is primarily utilized as a component of dry cell batteries and zinc–carbon batteries, where it is mixed with graphite to make cathodes. It is also used as an inorganic pigment in ceramics and glassmaking.