Psilomelane

Psilomelane is a historical collective name for hard, black manganese oxide minerals, especially romanechite and related barium-bearing manganese oxides. Its use reflects older mineral classification before these materials were distinguished as separate species.

Romanechite: A barium-bearing manganese oxide mineral with a tunnel structure and a major constituent of material historically called psilomelane. It is the principal modern mineral species associated with the historical name.
Tunnel structure: A crystal arrangement containing channels that can host water or other ions within a mineral framework. Tunnel frameworks characterize romanechite and several related minerals formerly called psilomelane.
Manganese ore: Rock or sediment containing enough manganese minerals to be economically extracted. Psilomelane-bearing material has been mined as a manganese ore.
Cryptomelane: A potassium-bearing manganese oxide mineral in the hollandite group, typically forming fine-grained or massive aggregates. It resembles material once grouped as psilomelane but is distinguished by composition and structure.
Hollandite: A barium-bearing manganese oxide mineral in the hollandite group, with a framework of manganese-oxide tunnels. It belongs to the family of hard, dark manganese oxides once grouped under broad names such as psilomelane.
Manganese oxide: A compound of manganese and oxygen, often forming minerals with complex structures and variable oxidation states. These compounds provide the chemical basis for the black material historically named psilomelane.
Manganese deposits: Natural concentrations of manganese minerals formed by geological, sedimentary, or hydrothermal processes. The historical name is encountered chiefly in descriptions of manganese-rich deposits.
Birnessite: A layered manganese oxide mineral, commonly fine-grained and able to incorporate water and other ions. Its layered structure contrasts with the tunnel structures of important psilomelane-associated minerals.
Manganese oxide minerals: Minerals composed chiefly of manganese and oxygen, often with water or other elements in their structures. Psilomelane names a historical grouping within this broad mineral family.
Weathering: The breakdown and alteration of rocks and minerals at or near Earth's surface. Oxidation and alteration during weathering can produce manganese-oxide coatings and accumulations.

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