At about the turn of the century, the Wrangell Mountains were traversed extensively by prospectors looking for either copper or gold, both of which were found in numerous places. Natives of the region, the Ahtna, were known to possess weapons and utensils made of pure copper. Prospectors finally located their sources of copper in 1899 and 1900, with the reluctant help of their leader, Chief Nicolai, bargaining to save his people who were starving from a harsh winter. When spotted from the glacier below, the ore weathering out along a ridge between the Kennicott Glacier and McCarthy Creek looked like a pasture of green grass. It turned out to be the richest (in concentration) copper lode ever found on earth!
There were numerous large and rich lodes trending toward the northeast, including the upward tapering main Bonanza vein. This wedge was 1900 feet (580 meters) long by 165 to 195 feet (50 to 60 meters) high by 1.5 to 50 feet (0.5 to 15 meters) wide. It alone yielded 720 thousand short tons (653 thousand metric tons) of ore grading 13% copper, and contained 15 short tons (14 metric tons) of silver. Near the base of the Jumbo vein was a single massive body of nearly pure chalcocite (chemical formula Cu2S, 80% copper by weight) measuring 325 by 65 by 50 feet (100 by 20 by 15 meters). Ores included carbonates malachite and azurite, sulfates covellite and chalcosite (sometimes also diginite), and native copper.
The Kennecott Mines Company was formed in 1906, with backing from J.P. Morgan and the Guggenheims, and later become the Kennecott Copper Corporation (both names containing a misspelling of "Kennicott"). The 14 story mill was assembled in 1907 from precut lumber brought in using horses, since there was then no railroad. Between 1908 and 1911, Michael J. Heney headed construction of the Copper River and Northwestern Railway, stretching 196 miles (314 km) between Kennicott and Cordova. Aerial tramlines carried ore from the mines to the mill for processing. Concentrate went by train from the mill to port, then was shipped by the Alaska Steamship Company to Tacoma (Washington) for smelting.
Some ore was so pure that no processing was required; but otherwise ore was concentrated by crushing, flotation, and leaching. The ammonia leaching process was refined and first used commercially on site at Kennicott. Over the lifetime of the mines, the ore averaged nearly 13% copper! By late 1938, when the mines closed and the last train headed south, over 591 thousand short tons (536 thousand metric tons) of copper and about 110 short tons (100 metric tons) of silver were produced. There were five mine sites (Mother Lode, Bonanza, Glacier, Jumbo, and Erie), and the length of underground tunnels reached 70 miles. The economic value of the copper exceeded that of all the gold in the Yukon Gold Rush!
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