Copper.
There are evidences that copper-mines were worked in the
United States by the
Mound-builders (q. v.). The first mines worked systematically were chiefly in
New Jersey and
Connecticut.
From 1709 until the middle of the eighteenth century, a mine at
Simsbury, Conn., yielded much ore, when, for about sixty years, the mine was a State prison.
The
Lake Superior copper-mines (the most considerable in the world) were first worked, in modern times, in 1845, when traces of ancient mining were found near the
Ontonagon River.
The Jesuit missionaries had noticed copper ore in that region as early as the middle of the seventeenth century.
In making excavations in 1848, a mass of copper, supported upon blocks of wood, with charred wood under it, was found 20 feet below the surface.
When taken out it weighed 8 tons.
The output of copper in the
United States during the calendar year 1899 amounted to 585,342,124 pounds, valued at $104,190,898. In that and the following year the output at the famous
Calumet and
Hecla and other mines in the
Lake Superior region, and at the mines at
Butte, Mont., was largely increased, and there was a remarkable development of copper-mining in many parts of the country where the metal had not been supposed to exist in paying quantities.
