Manganese dioxide, an inorganic compound with the chemical formula MnO2, is presented as either black amorphous powder or black rhombic crystals. It is poorly soluble in water, weak acids, weak bases, nitric acid, and cold sulfuric acid. Upon heating, it dissolves in concentrated hydrochloric acid.Cl₂Used in the preparation of manganese salts, also serves as an oxidizing agent, rust remover, and catalyst.

Manganese dioxide is a amphoteric oxide, existing in the form of salts with corresponding minerals like BaMnO3 or SrMnO3, which have a perovskite structure (obtained through compound reactions in the molten alkali system) [1], as well as in the form of manganese tetrachloride.