INTRODUCTION

 

THEN AND NOW AT THE KENNECOTT MINES

NATIONAL HISTORIC LANDMARK
 WRANGELL-ST. ELIAS NATIONAL PARK
AND PRESERVE, MC CARTHY, ALASKA



PHOTO GALLERY 1

It is a hike!  The famous Kennecott Mines, the Bonanza, Jumbo, Mother Lode, Glacier, and Erie, were located about 4,000 feet above the Kennecott mill town. Visitors to the Wrangell-St. Elias National Park and Preserve can follow three strenuous trails, each a full day for the round trip, to visit them.  For those unable to make the climb, these photo galleries will give you a glimpse of what you missed.

CLICK ON A PHOTOS TO ENLARGE

In this historic photo, the Bonanza tram towers can be seen starting the uphill journey to the mine on the ridgeline.  (Courtesy National Park Service)



CLICK ON THE IMAGE above!  In the enlarged view of this recent photo, the routes of the tramways can still be seen climbing the slopes behind the mill building.  (Courtesy US Geological Survey)

Bonanza Mine orebody was discovered 1900.  The outcrop of its ore was exposed high on the ridge top. The Kennecott Copper Corporation consolidated many of the claims in the area in 1905; however, it would take the construction of the 196-mile-long Copper River and Northwestern Railway to enable routine production to start.  The railroad provided access to the port of Cordova.  From there the Alaska Steamship Company transported the ore to a smelter in Tacoma, Washington.  First production at the Bonanza mine began in 1911. The Jumbo Mine started in 1913, the Glacier about the same time, and the Erie Mine in 1916.  The Mother Lode Mine was located on the other side of the ridge and operated by the Mother Lode Coalition Mines Company. It became part of the Kennecott operations in 1919.

It is an understatement to say that the Kennecott ore was fabulously rich. The principal ore mineral was chalcocite, along with malachite, azurite, and covellite.  Smaller amounts of enargite, bornite, chalcopyrite, and native copper were also found.  The ore contained an important silver byproduct. In some parts of the orebodies, large masses of pure chalcocite were mined.  This high-grade ore was shipped directly to the smelter without processing and averaged 50-55% copper.  Lower-grade ore was sent to the mill for processing.  The overall grade was over 12% copper. 

Mining the outcrop ore at the Bonanza Mine was done by open pit.  Underground mining was done in two stages using shrinkage stoping.  When possible, the high-grade ore was extracted first.  Then the lower-grade, mill ore was mined.  In both stages, the broken ore was drawn out of chutes and loaded into mine cars which carried the ore to the inclined shaft for hoisting to the surface.  The ore was then loaded into tramway buckets for the trip downhill to the mill.  In the mill, crushers and screens were used to reduce the ore to fine particles.  Then a variety jigs and shaking tables used gravity to separate the valuable minerals from the waste rock.  Mill tailings were disposed of in an area below the mill.  The concentrated ore and the direct shipping high-grade ore were loaded into bags for shipment by rail.  In 1916 an innovative ammonia leaching plant was constructed to further recover the copper oxides from the tailings.  In 1925, flotation was introduced to boost total recovery to 96%.

From 1911 to 1938, the Kennecott Mines produced 1.2 billion pounds of copper valued at $3.5 billion at today’s (October 2017) prices.  The mines themselves employed 200-300 workers, with an additional 300 employed in the mill and other townsite operations.  The wealth generated by the mines was used to develop several other important mines in the Lower 48 and overseas.  These include the Utah Copper Mine (Bingham Canyon), the Ray Mine in Arizona, the Chino Mine in New Mexico, the Nevada Consolidated Mine near McGill, and the Braden Mine (El Teniente) in Chile.    Extensive diamond drilling efforts at Kennecott failed to identify any additional orebodies and the mines were closed for good in 1938. 

While the harsh Alaskan winters have taken a toll on the buildings up high at the mines, the mill town of Kennecott survived six decades with much less degradation.  The Kennecott area was included in the Wrangel-St. Elias National Park and Preserve in 1980.  In 1986 the Kennecott complex was declared a National Historic Landmark.  Since that time, historic buildings and their contents have been carefully documented as part of the Historic American Buildings Survey (HABS)/Historic American Engineering Record (HAER).  Since 1998, the National Park Service has been stabilizing and restoring the historic structures as funding permits.  Those who visit the site are not only rewarded with a glimpse of this famous industrial outpost but also with a natural environment that is truly unique to Alaska.  For those unable to visit Kennecott, the Mining History Association website has a “virtual walking tour” of the town and the huge Kennecott Mill. 

(Adapted from “MINERALS COME FROM MINES: Profile of the Kennecott Mine in Alaska”

by L. Michael Kaas, Northern Virginia Gem and Mineral Club Newsletter, 2017)


(Above) The routes of the tramways are shown is red on this geologic map. (Moffit, 1918 with annotation by Kaas)

 

(Right) Kennecott Copper acquired the Mother Lode Mine in 1919.  Eventually all of the mines were interconnected through the drifts shown on the map.  (Douglas, 1967)

 


(Above) A plan view of the Jumbo, Bonanza, and Mother Lode Mine ore bodies.  (MacKevett, 1997)

 

(Right) A cross-section view of how the ore was extracted using shrinkage stoping. The high grade at the bottom of the vein was removed first and hoisted to the surface through the inclined shaft.  Then the mill grade ore was removed.  (Birch, 1924)


(Photos Courtesy National Park Service and US Geological Survey Photo Library)

CLICK HERE to “Visit” the Mines (Photo Galleries 2-6)

References and Web Links

F. H. Moffit and S. R. Capps, “Geology and Mineral Resources of the Nizina District, Alaska,” USGS Bulletin 448, (Washington: GPO, 1911).  https://pubs.usgs.gov/bul/0448/report.pdf


A. H. Brooks, “Mineral Resources of Alaska,” USGS, Bulletin 662, (Washington: GPO, 1918).  https://pubs.usgs.gov/bul/0662/report.pdf

 

F. H. Moffit, “Mining in the Copper River Basin,” USGS, Bulletin 662c, (Washington: GPO, 1918). https://pubs.usgs.gov/bul/0662c/report.pdf

 

Stephen Birch, “Geology and Mining Methods of Kennecott Mines,” Mining and Metallurgy, (New York: AIME, 1924).

 

Douglass, William C., “A History of the Kennecott Mines, Kennecott, Alaska,” Alaska Division of Mines and Minerals, Miscellaneous Publication 21, October 1964.  (http://doi.org/10.14509/723, accessed 22 March 2018)

 

William R. Hunt, “Golden Places: The History of Alaska-Yukon Mining,” Chapter 13, Kennecott and Other Mines. (Anchorage, Alaska: National Park Service, 1990).  (https://www.nps.gov/parkhistory/online_books/yuch/golden_places/chap13.htm, accessed 22 March 2018)

 

Edward M. MacKevett, Jr., et al, “Mineral Deposits and Occurrences in the McCarthy Quadrangle, Alaska,” in Mineral Deposits of Alaska: Economic Geology Monograph 9, R. J. Goldfarb and Lance D. Miller, eds. (New Haven: Economic Geology Publishing Company, 1997). (Alaska Mining Hall of Fame, http://alaskamininghalloffame.org/inductees/mackevett.php, accessed April 23, 2018)

 

Charles C. Hawley, “A Kennecott Story: Three Mines, Four Men, and One Hundred Years, 1887-1997,” (Salt Lake City: University of Utah Press, 2014).

 

 


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