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Native copper is an uncombined form of copper which 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 of copper in historic times and was used by pre-historic peoples. Native copper occurs rarely as isometric cubic and octahedral crystals, but more typically as irregular masses and fracture fillings. It has a reddish, orangish, and/or brownish color on fresh surfaces, but typically is weathered and coated with a green tarnish of copper(II) carbonate (also known as patina or verdigris). Its specific gravity is 8.9 and its hardness is 2.5–3.〔(【引用サイトリンク】title=Native Copper )〕 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.〔 (Web archive; click cancel when it asks for authentication.)〕 Native Americans mined copper on a small scale at this and several other locations, and evidence exists of copper trading routes throughout North America among native peoples, proven by isotopic analysis. The first commercial mines in the Keweenaw 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.〔 Another major native copper deposit is in Coro Coro, Bolivia. The name copper comes from the Greek ''kyprios'', of Cyprus, the location of copper mines since pre-historic times.〔 ==Gallery== File:Copper-20856.jpg|Broken Hill, New South Wales, Australia File:Copper-130051.jpg|Native copper cementing host rock, Ray Mine, Arizona File:Copper-20862.jpg|Itauz Mine, Kazakhstan File:Copper-18705.jpg|Tsumeb, Namibia File:Copper-Gypsum-177370.jpg|Dendritic native copper encased in transparent gypsum, Mission Mine, Pima County, Arizona, USA File:Copper-Silver-39566.jpg|"Halfbreed" copper-silver nugget, Keweenaw County, Michigan, USA File:Native Copper from the Keweenaw Peninsula Michigan.jpg|Native Copper, Keweenaw Peninsula, Michigan, USA 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「native copper」の詳細全文を読む スポンサード リンク
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