Native copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

, as native copper, is one of the few metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

lic element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

s to occur in uncombined form
Native Metal
A native metal is any metal that is found in its metallic form, either pure or as an alloy, in nature. Metals that can be found as native deposits singly and/or in alloys include aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, nickel, selenium, tantalum, tellurium,...

 as a natural mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

, although most commonly occurs in oxidized states and mixed with other elements. Native copper was an important ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....

 of copper in historic times and was used by pre-historic peoples.

Native copper occurs as rarely 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
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...

 and coated with a green tarnish
Tarnish is a thin layer of corrosion that forms over copper, brass, silver, aluminum, and other similar metals as their outermost layer undergoes a chemical reaction. Tarnish does not always result from the sole effects of oxygen in the air. For example, silver needs hydrogen sulfide to tarnish; it...

 of copper(II) carbonate
Copper(II) carbonate
Copper carbonate is a blue-green compound forming part of the verdigris patina that is found on weathered brass, bronze, and copper. The colour can vary from bright blue to green, because there may be a mixture of both copper carbonate and basic copper carbonate in various stages of hydration...

 (also known as patina
Patina is a tarnish that forms on the surface of bronze and similar metals ; a sheen on wooden furniture produced by age, wear, and polishing; or any such acquired change of a surface through age and exposure...

 or verdigris
Verdigris is the common name for a green pigment obtained through the application of acetic acid to copper plates or the natural patina formed when copper, brass or bronze is weathered and exposed to air or seawater over a period of time. It is usually a basic copper carbonate, but near the sea...

). Its specific gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...

 is 8.9 and its hardness is 2.5–3.

The mines of the Keweenaw native copper deposits of Upper Michigan
Upper Peninsula of Michigan
The Upper Peninsula of Michigan is the northern of the two major land masses that make up the U.S. state of Michigan. It is commonly referred to as the Upper Peninsula, the U.P., or Upper Michigan. It is also known as the land "above the Bridge" linking the two peninsulas. The peninsula is bounded...

 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 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
Keweenaw Peninsula
The Keweenaw Peninsula is the northern-most part of Michigan's Upper Peninsula. It projects into Lake Superior and was the site of the first copper boom in the United States. As of the 2000 census, its population was roughly 43,200...

 (which is nicknamed the "Copper Country
Copper Country
The Copper Country is an area in the Upper Peninsula of Michigan in the United States, including all of Keweenaw County, Michigan and most of Houghton, Baraga and Ontonagon counties. The area is so named as copper mining was prevalent there from 1845 until the late 1960s, with one mine ...

" and "Copper Island
Copper Island
Copper Island is a local name given to the northern part of the Keweenaw Peninsula , separated from the rest of the Keweenaw Peninsula by Portage Lake and the Keweenaw Waterway.- Geography :The area was "isolated" by dredging in 1859 and construction in the...

"), opened in the 1840s. Isle Royale
Isle Royale
Isle Royale is an island of the Great Lakes, located in the northwest of Lake Superior, and part of the state of Michigan. The island and the 450 surrounding smaller islands and waters make up Isle Royale National Park....

 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
Coro Coro, Bolivia
Coro Coro, Bolivia is a a location in the La Paz Department in Bolivia. It is the seat of the Coro Coro Municipality, the first municipal section of the Pacajes Province, and it is the seat of the province....


The name copper comes from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 kyprios, of Cyprus
Cyprus , officially the Republic of Cyprus , is a Eurasian island country, member of the European Union, in the Eastern Mediterranean, east of Greece, south of Turkey, west of Syria and north of Egypt. It is the third largest island in the Mediterranean Sea.The earliest known human activity on the...

, the location of copper mines since pre-historic times.

Further reading

  • Thurner, Arthur W. Strangers and Sojourners - A History of Michigan's Keweenaw Peninsula (Detroit, Michigan, U.S.A.: Wayne State University Press, 1994) ISBN 0814323960.B
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