Manganese dioxide is known as the inorganic compound that bears the formula MnO. It is a blackish or brownish solid that occurs naturally with the mineral pyrolusite. It is the main ore of manganese, and one of the central components of manganese nodules. There are a variety of uses for this compound, but the most common is for the creation of dry cell batteries. This includes things such as the alkaline battery and a variety of zinc carbon batteries. The compound is also frequently used as a pigment, especially in early parts of human history, where it was used as a painting compound for cave paintings and body paint. Many chemists use it as a precursor for other manganese compounds as well, including KMnO. It is often used as a reagent for organic synthesis, including in the oxidation of various allylic alcohols. This compound can stain human skin if the user is not careful.