Psilomelane
Psilomelane is a group name for 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.
| Psilomelane | |
|---|---|
| General | |
| Category | Oxide minerals |
| Formula (repeating unit) | General formula: Ba(Mn2+)(Mn4+)8O16(OH)4, or as (Ba,H2O)2Mn5O10 Barium manganese oxide hydroxide |
| Crystal system | Monoclinic |
| Identification | |
| Formula mass | 590.03 g/mol |
| Color | Black with gray pyrolusite bands |
| Crystal habit | Botryoidal, mammillary, reniform |
| Cleavage | None |
| Fracture | Conchoidal and uneven |
| Mohs scale hardness | 5.0 – 6.0 |
| Luster | Sub-metallic, dull |
| Streak | Brownish black |
| Diaphaneity | Opaque |
| Specific gravity | 3.7 – 4.7 |
| Polish luster | Vitreous to subadamantine |
| Solubility | in hydrochloric acid |
| Other characteristics | Hard black manganese oxides such as hollandite and romanechite |
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