| Copper | |
|---|---|
 Native copper from Ray mine,Arizona (specimen 5.25 x 4 x 1 cm) | |
| General | |
| Category | Native metal |
| Formula | Cu |
| Strunz classification | 01.AA.05 |
| Dana classification | 1.1.1.3 |
| Crystal system | Cubic |
| Crystal class | Hexoctahedral (m3m) H-M symbol: (4/m3 2/m) |
| Space group | Fm3m |
| Unit cell | a = 3.615 Å; Z = 4 |
| Identification | |
| Color | Pale rose on fresh surface, quickly darkens to copper-red; in reflected light, pale rose |
| Crystal habit | As cubes, dodecahedra, and as tetrahexahedra; rarely as octahedra and complex combinations. Commonly flattened on {111}, elongated along [001]. Also as irregular distortions, in twisted, wirelike shapes; filiform, arborescent, massive |
| Twinning | On {111} to produce simple contact and penetration twins and cyclic groups |
| Cleavage | None |
| Fracture | Hackly - jagged |
| Tenacity | Highly malleable and ductile |
| Mohs scale hardness | 2+1⁄2–3 |
| Luster | Metallic |
| Streak | Copper-red |
| Diaphaneity | Opaque |
| Specific gravity | 8.95 |
| Solubility | Soluble innitric acid |
| Other characteristics | Tarnishes to black or green in air. |
| References | [1][2][3][4] |
Native copper is anuncombined form ofcopper that occurs as a naturalmineral. Copper is one of the fewmetallicelements to occur innative form, although it most commonly occurs inoxidized states and mixed with other elements. Native copper was an importantore of copper in historic times and was used by pre-historic peoples.
Native copper occurs rarely as isometric cubic andoctahedral crystals, but more typically as irregular masses andfracture fillings. It has a reddish, orangish, and/or brownish color on fresh surfaces, but typically isweathered and coated with a greentarnish ofcopper(II) carbonate (also known aspatina orverdigris). Itsspecific gravity is 8.9 and itshardness is 2.5–3.[5]
The mines of theKeweenaw native copper deposits ofUpper Michigan were major copper producers in the 19th and early 20th centuries, and are the largest deposits of native copper in the world.[6] Native Americans mined copper on a small scale at this and many other locations,[7] and evidence exists of copper trading routes throughout North America among native peoples, proven by isotopic analysis. The first commercial mines in theKeweenaw Peninsula (which is nicknamed the "Copper Country" and "Copper Island") opened in the 1840s.Isle Royale in western Lake Superior was also a site of many tons of native copper. Some of it was extracted by native peoples, but only one of several commercial attempts at mining turned a profit there.[6] An archived record of native copper originally found up river fromLake Superior, on the west branch of theOntonagon River, via being dragged by aglacier is seen in theOntonagon Boulder now in the possession of the Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution.
Another major native copper deposit is inCoro Coro, Bolivia.
The name copper comes from theGreekkyprios, "ofCyprus", the location of copper mines since pre-historic times.[3]
