MINERAL OF THE MONTH
January 2008: Native Copper
January’s mineral of the month is native copper. This interesting specimen was recently donated to the museum by Peter Pagel, from Marquette. He acquired it from the Houghton area. It is a thick slab of native copper in matrix that is 7 inches by 6 inches.
This specimen was mined from the Keweenaw Peninsula, which is the greatest native copper ore deposit ever found on earth. The deposit formed in the Mid-continent rift zone around a billion years ago. Native Americans have been mining the ore since around 3000 B.C. The first written account of copper was provided by French missionary Claude Allouez in 1667. He recorded that Indians of the Lake Superior region mined copper nuggets in shallow depressions. It was these abandoned pits that led early American prospectors to the sites where successful mines were later established. Large scale mining operations began in 1844 and continued until the 1960s when open pit mining out west became more profitable than underground mining.
The first person to report on the commercial potential of the copper deposit was state geologist, Douglass Houghton, in 1841. The Cliff mine, which was the first copper mine establised in Michigan, began operations in 1845. Copper mining in northern Michigan boomed, and from 1845 until 1887 (when it was exceeded by Butte, Montana) Michigan was the nation's leading producer of copper. In most years from 1850 through 1881, Michigan mined more than three-quarters of the nation's copper, and in 1869 produced more than 95% of the country's copper. Annual production peaked in 1916 at 266 million pounds. Most of the native copper mines shut down in 1968, after producing 11 billion pounds of copper. The White Pine Mine operated until 1995. The only mine still mining copper on a small scale is the Caladonia Mine, located 20 miles northeast of Ontonogon. The mine’s owner, Richard Whiteman, has a worth-the-stop gift shop in Ontonogon called the Gitche Gumee Landing, located at 202 Ontonagon Street, 906-884-6618, www.caledoniamine.com.
The Keeweenaw deposit occurs in an area around 110 miles long, 10 miles wide, and up to a 1,000 feet deep. Throughout this area, there are amgadaloid (basaltic pocket) deposits as well as veins with copper ranging in size from microscopic grains to very large masses of up to around 1,200,000 pounds. Float copper specimens can also be found throughout the Midwest that were scraped free and deposited by Pleistocene glaciers that scoured the Keeweenaw Peninsula during the various ice ages.
One of the most interesting facts about the Keeweenaw copper is that it occurs in a fairly pure metal form called native copper. Most of the other copper deposits in the world form as copper oxides or copper sulfides that require processing to extract the copper.
Copper is a chemical element with the symbol Cu and atomic number 29. It is used extensively as an electrical conductor, heat conductor, building material, and component of various alloys. Copper is a reddish-colored metal that has its characteristic color because of its band structure. In its liquefied state, pure copper appears somewhat greenish, a characteristic shared with gold. When liquid copper is in bright ambient light, it retains some of its pinkish luster.
Civilizations in places such as Iraq, China, Egypt, Greece, India and the Sumerian cities all have early evidence of using copper. A copper pendant was found in northern Iraq that dates to 8700 BC. During the Roman Empire, copper was principally mined on Cyprus, hence the origin of the name of the metal as Cyprium, "metal of Cyprus", later shortened to Cuprum. High demand relative to supply has caused the price of copper to spike during the last few years.
It has been reported that copper is an excellent conductor that amplifies thoughts, boosts confidence, and facilitates healing. It has been used to treat arthritis as well as other inflammation and circulatory diseases.
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Gitche Gumee Museum.
E21739 Brazel Street
Grand Marais, Michigan 49839