Coronadite
Coronadite is a black lead that is metallic oxide mineral that is a part of the Coronadite Group of minerals that also includes Hollandite, among others. Coronadite gems are somewhat unusual only because there is little demand for them other than as an collector gem that is unusual. Faceted gems are rather attractive however, with dark gray to color that is black submetallic luster that looks white in reflected light.
Coronadite was first described and called in 1904 by Waldemar Lindgren and William F. Hillebrand from material on the dump of a mine that is little on the west end of the Coronado vein, three-fourths of a mile western of Horseshoe shaft for the Coronado Mine, Clifton-Morenci region, Greenlee County, Arizona, United States Of America. Lindgren and Hillebrand proposed the name “Coronadite” to honor Francisco Vasquez de Coronado (1510-1554), a conquistador that is spanish explorer of the American southwest who had visited the location in 1540. Hillebrand said: “We propose the name Coronadite, following the famous explorer of this portion of the continent that is american which the Territories of New Mexico and Arizona are formed.” They described Coronadite as “a black mineral that is metallic maybe not unlike Psilomelane in basic appearance, and intemately intermixed with Quartz, can be found in fairly large amount into the Coronado vein.”
Coronadite distribution: Widespread; several localities for pure or product that is well-characterized: in the United States Of America, in Arizona, through the Coronado vein, Clifton-Morenci district, Greenlee County; the Magma mine, Superior, Pinal County; through the Artillery Mountains, Mohave County, and elsewhere. In New Mexico, from the Luis Lopez district, Socorro County. From the Philipsburg district, Granite County, Montana. In Mexico, from the Talamantes district, Chihuahua, and in the Ojuela mine, Mapimí, Durango. At many places within the Ouarzazate and Oujda districts, and elsewhere in Morocco. From the Almalyskoye Pb–Zn deposit, Kurgashikan, Uzbekistan. In the Dry Gill mine, Caldbeck Fells, Cumbria, England. In France, from the Richesse mine, near Bourgeten-Huile, Savoy. At Dongari Buzurg, Bhandara, Madhya Pradesh, and Kodur, Andhra Pradesh, India. From Broken Hill, brand new South Wales, plus in the Puttapa zinc mine, near Beltana, South Australia. At Tsumeb, Namibia.
| Chemical Formula: | Pb(Mn4+,Mn2+)8O16 |
| Lead Manganese Oxide | |
| Molecular Weight: | 933.55 gm |
| Composition: | Barium | 1.47 % | Ba | 1.64 % | BaO |
| Manganese | 45.31 % | Mn | 3.80 % | MnO / 67.05 % MnO2 | |
| Aluminum | 0.29 % | Al | 0.55 % | Al2O3 | |
| Vanadium | 1.09 % | V | 1.95 % | V2O5 | |
| Lead | 24.41 % | Pb | 26.30 % | PbO | |
| Oxygen | 27.42 % | O | |||
| 100.00 % | 101.29 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | As fibrous botryoidal aggregates, banded with other manganese oxides; as microscopic curved lamellae; laminated, granular, massive. |
| Twinning: | None |
| Cleavage: | n/a |
| Fracture: | n/a |
| Tenacity: | Brittle |
| Moh’s Hardness: | 4.5 – 5.0 |
| Density: | 5.246 – 5.505 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Dark gray to black; white in reflected light |
| Transparency: | Opaque |
| Luster: | Dull to submetallic |
| Refractive Index: | Biaxial |
| Birefringence: | 0.000 (opaque) |
| Dispersion: | Strong; r > v |
| Pleochroism: | Strong; dark brown to gray |
| Anisotropism: | Strong; nearly Galena-white |
