Ann: Presentation at Africa Downunder 2013 Confer, page-3

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"The Keweenaw Peninsula is the site of the most extensive known deposits of native copper in the world. Occurring here in relatively pure form, the red metal could be broken out of the rock and worked to make a wide variety of products, from jewelry and tools by its earliest miners to coins and electric wire by its final generations. Keweenaw copper was mined for approximately 7,000 years, from 5000 BCE until 1968. During the period for which records were kept, 1840–1968, more than 11 billion pounds (5 million metric tons) of copper were mined here. During the peak production years of World War I, 1916–1917, the annual copper yield reached a maximum of 270 million pounds (125,000 t)."