A Simplified Scheme for Polymorphism in the Manganese Dioxides

Abstract

In order to clarify how many MnO₂ modifications exist, the author has investigated the cryptocrystalline manganese dioxides and oxyhydroxides. He finds that only ramsdellite and pyrolusite (=polianite, β-MnO₂) are true MnO₂ modifications, and that the nsutite (γ-MnO₂) family includes a series of intergrowth structure varieties. While the nsutite family is structurally related to the true MnO₂ modifications, the birnessite and the hollandite families are distinctly differing in structure from one another as well as from ramsdellite, pyrolusite and nsutite. A simplified scheme of these compounds, finally, is proposed.