Psilomelane
Psilomelane is an obsolete group name and general term for hard, black manganese (Mn) oxide minerals. The chemical formula of Psilomelane is BaMn2+Mn4+8O16(OH)4 (Barium manganese hydroxide) and its molecular weight is 590.03 gm. Romanèchiteis the primary constituent of Psilomelane, which is a mixture of minerals. Psilomelane has a specific gravity of 4.40 – 4.72 (g/cm3) and the refractive index of NCalc = 2.11 – 2.26. Moh’s Hardness is 5.0 – 6.0. Psilomelane is often layered with gray Pyrolusite creating bands of metallic gray and sub-metallic black. The material from a recent find at the Silver Crown Mine, Chihuahua, Mexico is particularily attractive with dark gray and black bands, swirls and patterns. Psilomelane is similar in appearance to Hematite, except for the swirls and patterns.
| Category: | Oxide minerals |
| Chemical Formula: | BaMn2+Mn4+8O16(OH)4 |
| Barium manganese hydroxide |
|
| Molecular Weight: | 590.03 gm |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Commonly massive, botryoidal, stalactitic and can also be found as earthy crusts or massive. |
| Composition: | Barium | 23.27 % | Ba | 25.99 % | BaO |
| Manganese | 46.56 % | Mn | 66.89 % | Mn2O3 | |
| Hydrogen | 0.34 % | H | 3.05 % | H2O | |
| Oxygen | 29.83 % | O | |||
| 100.00% | 100.00% | =TOTAL OXIDE |
| Cleavage: | None |
| Fracture: | Uneven |
| Tenacity: | Brittle |
| Moh’s Hardness: | 5.0 – 6.0 |
| Density: | 4.40 – 4.72 (g/cm3) |
| Radioactivity: | Not Radioactive |
| Color: | Iron Black, Dark Steel Gray |
| Transparency: | Opaque |
| Luster: | Sub-Metallic, Dull |
| Refractive Index: | NCalc = 2.11 – 2.26 |
| Birefringence: | n/a |
| Dispersion: | n/a |
| Pleochroism: | None |
