Pyrolusite

Pyrolusite is a manganese dioxide mineral, MnO₂, and the most important natural ore of manganese. It commonly occurs as black, fine-grained or fibrous material.

Manganese dioxide: Manganese dioxide is an inorganic compound with the formula MnO₂, occurring in several mineral and synthetic forms. Pyrolusite is the crystalline mineral form most commonly associated with this compound.
Oxidation state: An oxidation state is a bookkeeping value describing an atom's electron balance in a chemical species. Manganese is in the +4 oxidation state in MnO₂, enabling reduction in several reactions.
Ferromanganese: Ferromanganese is an iron–manganese alloy used to add manganese to steel and remove oxygen and sulfur. Manganese extracted from pyrolusite commonly enters steelmaking through this alloy.
Dendrite (mineralogy): A mineral dendrite is a branching, tree-like deposit formed by mineral growth along fractures or surfaces. Pyrolusite commonly forms dark dendritic coatings that resemble plant markings.
Manganese: Manganese is a chemical element with atomic number 25, used widely in steelmaking and batteries. Pyrolusite is the principal natural source from which manganese is extracted.
Redox reaction: A redox reaction transfers electrons between chemical species, changing their oxidation states. Pyrolusite acts as an oxidant when manganese(IV) is reduced.
Dry cell: A dry cell is a primary electrochemical battery whose electrolyte is held in a paste or other nonflowing medium. Manganese dioxide from pyrolusite is used as a depolarizing cathode material in traditional dry cells.
Psilomelane: Psilomelane is an obsolete collective name for hard, black, commonly barium-bearing manganese oxides. Its dark massive appearance has often led to confusion with pyrolusite.
Rutile structure: The rutile structure is a tetragonal crystal arrangement found in minerals including rutile and pyrolusite. Pyrolusite's crystal structure belongs to this mineral structure type.
Electrolysis: Electrolysis uses electrical current to drive a nonspontaneous chemical reaction. Electrolytic manganese production can use manganese dioxide as a feedstock.

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