Tenorite
Tenorite is a rare secondary copper oxide mineral that is rarely faceted. It is one of those gems for “black gem” collectors. It is usually opaque black with a metallic luster and fairly soft. Large, pure crystals for faceting are rare and typically found only as thin (2mm), scaley, lathlike crystals. Most locations produce Tenorite mixed with Azurite and Malachite. A recent find at the L’Etoile du Congo Mine (Star of the Congo Mine) and the Kalukuluku Mine, Lubumbashi (Elizabethville), Shaba, Congo (Zaïre) has produced some larger, pure crystals.
Although Tenorite is cited as being discovered in 1841 in Vesuvio (Vesuvius), Napoli, Campania, Italy, it was first referrenced by Abraham Gottlob Werner (1749-1817) in 1789 as Kupferschwärze, which means black copper in German. Tenorite was named in 1841 by Prof. Giovanni Semmola in honor of Italian botanist, Prof. Michele Tenore (1780-1861), Professor of Botany, University of Naples, Italy.
Tenorite distribution: many localities, but few for well-crystallized or pure material. From Vesuvius, Campania, and Etna, Sicily, Italy. In England, at a number of mines in Gwennap, Redruth, St. Just, and elsewhere in Cornwall. At Leadhills, Lanarkshire, Scotland. From Rio Tinto, Huelva Province, Spain. In Germany, at Siegen, Westphalia; from Daaden, Rhineland-Palatinate; and at Neubulach, Black Forest. At Jáchymov (Joachimsthal), Czech Republic. In Russia, from Bogoslovsk and Nizhni Tagil, Ural Mountains, and at the Tolbachik fissure volcano, Kamchatka Peninsula. In the USA, from Copper Harbor, Keweenaw County, Michigan; at Darwin, Inyo County, California; an ore at Bisbee, Cochise County, Arizona. From Chuquicamata, Antofagasta, Chile. At Tsumeb, Namibia.
| Chemical Formula: | CuO |
| Copper Oxide | |
| Molecular Weight: | 79.55 gm |
| Composition: | Copper | 79.89 % | Cu | 100.00 % | CuO |
| Oxygen | 20.11 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Lathlike crystals, flattened on [100], elongated along [011], to 2 mm; curved, scaly, dendritic; commonly pulverulent, earthy, massive. |
| Twinning: | On {011}, contact plane, common, forming stellate groups; lamellar. |
| Cleavage: | Poor/indistinct in zone [011] |
| Fracture: | Irregular/uneven, conchoidal |
| Tenacity: | Brittle; flexible and elastic in thin scales |
| Moh’s Hardness: | 3.5 – 4.0; Vickers: VHN100=190-300 kg/mm2 |
| Density: | 6.45 – 6.50 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Black, steel gray |
| Transparency: | Opaque; translucent on very thin edges |
| Luster: | Metallic |
| Refractive Index: | 2.10 – 2.11 Biaxial ( ? ) |
| Birefringence: | Anisotropic |
| Dispersion: | n/a |
| Pleochroism: | Weak; X = light brown, Z = dark brown |
| Anisotropism: | Strong: blue to gray; bireflectance: strong, light gray with golden hint |
