Psilomelane 18x13mm Oval Cabochon

Psilomelane describes a group of hard black manganese oxides, including Hollandite and Romanechite. Psilomelane consists of hydrous manganese oxide with variable amounts of barium and potassium. Psilomelane is erroneously, and uncommonly, known as black hematite, despite not being related to true hematite, which is an iron oxide.