Native copper
Native copper is an uncombined form of copper that occurs as a natural mineral. Copper is one of the few metallic elements to occur in native form, although it most commonly occurs in oxidized states and mixed with other elements. Native copper was an important ore used by pre-historic peoples. Native copper typically occurs as irregular masses and fracture fillings, and rarely as isometric cubic and octahedral crystals. It has a reddish, orangish, and/or brownish color on fresh surfaces, but typically is weathered to a state of verdigris and coated with a green or blue-green tarnish or patina of copper(II) carbonate. Its specific gravity is 8.9 and Mohs hardness is 2.5–3. The mines of the Keweenaw native copper deposits of Upper Michigan were major copper producers in the 19th and early 20th centuries, and are the largest deposits of native copper in the world. Native Americans mined copper on a small scale at this and many other locations, and evidence using isotopic analysis exists of copper trading routes throughout North America among native peoples. The first commercial mines in the Keweenaw Peninsula (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. A geological record of native copper being dragged by a glacier and deposited on the west branch of the Ontonagon River up river from Lake Superior is seen in the Ontonagon Boulder in the possession of the Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution. Another major native copper deposit is in Coro Coro, Bolivia.
| 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/m 3 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 | 2.5–3 |
| Luster | Metallic |
| Streak | Copper-red |
| Diaphaneity | Opaque |
| Specific gravity | 8.95 |
| Solubility | Soluble in nitric acid |
| Other characteristics | Tarnishes to black or green in air. |
| References | [1][2][3][4] |
Native copper is an uncombined form of copper that occurs as a natural mineral. Copper is one of the few metallic elements to occur in native form, although it most commonly occurs in oxidized states and mixed with other elements. Native copper was an important ore used by pre-historic peoples.
Native copper typically occurs as irregular masses and fracture fillings, and rarely as isometric cubic and octahedral crystals. It has a reddish, orangish, and/or brownish color on fresh surfaces, but typically is weathered to a state of verdigris and coated with a green or blue-green tarnish or patina of copper(II) carbonate. Its specific gravity is 8.9 and Mohs hardness is 2.5–3.[5]
The mines of the Keweenaw native copper deposits of Upper 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 using isotopic analysis exists of copper trading routes throughout North America among native peoples. The first commercial mines in the Keweenaw Peninsula (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] A geological record of native copper being dragged by a glacier and deposited on the west branch of the Ontonagon River up river from Lake Superior is seen in the Ontonagon Boulder in the possession of the Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution.
Another major native copper deposit is in Coro Coro, Bolivia.
Gallery
[edit]- Specimens from notable native copper localities worldwide
-
-
Native copper cementing host rock, Ray Mine, Arizona (11.5 x 7.4 x 0.7 cm) -
Dendritic native copper from the Itauz Mine, Kazakhstan (8 x 3 x 1.5 cm) -
Tsumeb, Namibia (3 x 1.3 x 0.5 cm) -
Dendritic native copper encased in transparent gypsum, Mission Mine, Pima County, Arizona, US (9.9 x 4.2 x 1.1 cm) -
"Halfbreed" copper-silver nugget, Keweenaw County, Michigan, US (8.3 x 4.6 x 2 cm) -
Keweenaw Peninsula, Michigan, US (6.4 cm) -
Native copper with verdigris, Keweenaw Peninsula, Michigan, USA. (4.1 cm)
See also
[edit]- Native element mineral – Elements that occur in nature as minerals in uncombined form
- Noble metal – Metallic elements that are nearly chemically inert
- Gangue – Commercially worthless material that surrounds a wanted mineral in ore
- Native state (metallurgy) – Form of metal
References
[edit]- ^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Copper" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 4 July 2022.
- ^ Copper, WebMineral.com, retrieved 2009-12-04
- ^ "Copper". mindat.org. Retrieved 2009-12-04.
- ^ Klein, Cornelis and Cornelius S. Hurlbut, Manual of Mineralogy, Wiley, 20th ed., 1985, pp 259-260 ISBN 0-471-80580-7
- ^ "Native Copper". Amethyst Galleries' Mineral Gallery. Archived from the original on 2005-06-28. Retrieved 2005-06-26.
- ^ a b "Michigan's Copper Deposits and Mining". Archived from the original on 2005-09-09. Retrieved 2005-06-26. (Web archive; click cancel when it asks for authentication.)
- ^ Henry Rowe Schoolcraft and Seth Eastman (1851). Historical and statistical Information, respecting the History, Condition and Prospects of the Indian Tribes of the United States: Coll. and prepared under the direction of the Bureau of Indian Affairs per act of Congress of march 3rd 1847, Volume 1. Lippincott, Grambo. pp. 223–229. ISBN 9781298905062. Retrieved July 17, 2011.
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Further reading
[edit]- Thurner, Arthur W. Strangers and Sojourners - A History of Michigan's Keweenaw Peninsula (Detroit, Michigan, U.S.A.: Wayne State University Press, 1994) ISBN 0-8143-2396-0.B
- "Prehistoric Copper in Wisconsin". Mississippi Valley Archaeology Center. Archived from the original on 2005-08-30. Retrieved 2005-06-26.
External links
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