Romanèchite
Romanèchite is a barium manganese oxide mineral. It is the primary constituent of Psilomelane, which is a mixture of minerals. Romanèchite is commonly found associated with Pyrolusite and other manganese oxide minerals as well as Goethite, Calcite, and Quartz. Romanèchite is a valuable ore of manganese, which is an essential ingredient in steel and other alloys. It is opaque, black to dark steel-gray with sub-metallic luster and a Moh’s hardness of 5 – 6. Romanèchite specimens of black, lustrous, botryoidal masses can be quite attractive. Faceted Romanèchite gems are rare and unusual.
Romanèchite distribution: although common in occurrence, characterization by X-ray, chemical analysis, or both, is necessary. Authenticated from: Romanèche, Saône-et-Loire, France. In Germany, well-crystallized from Schneeberg, Saxony, and at the Clara Mine, near Oberwolfach, Black Forest. From the Restormel mine, Lostwithiel, Cornwall, England. In the USA, at Austinville, Wyeth County, Virginia; from Sodaville, Mineral County, Nevada; at the Hoggett mines, Hidalgo County, New Mexico; at the Tolbard mine, Paymaster district, Imperial County, California. In the Talmantes mine, near Parral, Chihuahua, Mexico. From Pilbara, Western Australia.
| Category: | Oxide minerals |
| Chemical Formula: | (Ba, H2O)2Mn5O10 |
| Hydrated Barium Manganese Oxide | |
| Molecular Weight: | 544.25 gm |
| Composition: | Barium | 17.66 % | Ba | 19.72 % | BaO |
| Manganese | 48.45 % | Mn | 69.62 % | Mn2O3 | |
| Silicon | 0.52 % | Si | 1.10 % | SiO2 | |
| Hydrogen | 0.44 % | H | 3.97 % | H2O | |
| Oxygen | 34.92 % | O | |||
| 100.00 % | 94.41 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Euhedral crystals very rare, flat, ridged, to 200 μm; acicular to fibrous, divergent; commonly reniform, botryoidal, stalactitic, colloform banded; very fine-grained massive. |
| Twinning: | None |
| Cleavage: | None |
| Fracture: | Irregular/uneven |
| Tenacity: | Brittle |
| Moh’s Hardness: | 5.0 – 6.0; Vickers: VHN100=514-715 kg/mm2 |
| Density: | 4.70 – 4.74 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Iron-black, dark steel-gray; gray-white in reflected light |
| Transparency: | Opaque |
| Luster: | Sub-metallic, dull when massive |
| Refractive Index: | R1–R2: (400) 26.7–38.7, (420) 26.3–37.7, (440) 25.6–35.9, (460) 25.2–34.8, (480) 24.8–34.0, (500) 24.3–33.0, (520) 23.8–32.1, (540) 23.4–31.1, (560) 22.9–30.1, (580) 22.4–29.3, (600) 22.0–28.6, (620) 21.6–28.0, (640) 21.3–27.5, (660) 21.2–27.2, (680) 20.9–26.8, (700) 20.7–26.5
Biaxial |
| Birefringence: | None |
| Dispersion: | None |
| Pleochroism: | None |
| Anisotropism: | Strong. Bireflectance: Strong; gray to white. |
