2006 Mining History Association Tour

Phelps Dodge Morenci Open Pit Mine

Morenci, Arizona

June 4, 2006


The history of mining in Morenci, Arizona is still being written.  It is one of the largest mining and processing complexes in the world.  Fortunately, many excellent books and articles are available that tell the story of its discovery and development, the many important people involved, and the technological innovations made there.  This overview provides only an introduction.


The earliest mineral discoveries in the Morenci area were made in the late 1860s and early 1870s by area ranchers chasing Indian raiders and prospecting for gold.  By 1872 work had begun at the Arizona Central, Longfellow, Metcalf, and Yankie claims.  The Longfellow Mining Company was formed in 1874.  A mining camp was established in 1875 at what was to become the town of Metcalf.  The early oxide ores were very high grade, about 20% copper. 
Steep inclines were built to lower ore cars from the mines on the high slopes to Chase Creek. 
A smelter was built in Clifton, Arizona in 1874.  In 1879, the Coronado Railroad, a 20 inch, baby gauge, was constructed to link the base of the Longfellow Mine incline to the smelter.  In 1880, a steam engine replaced mule power.  The railroad continued to operate until 1922.  In1882 these operations were sold to a Scottish firm, the Arizona Copper Company.

Longfellow Mine and Concentrator, 1901
(Courtesy Phelps Dodge


The Arizona Copper Company greatly expanded its operations with a rail link to Lordsburg, New Mexico, a new smelter in Clifton, and an extension of the Coronado Railroad to the Metcalf and Coronado Mines.  Cost overruns caused the company to mortgage  itself, but it survived the financial crisis.  In 1886, it built a concentrator near the  Clifton smelter. Copper prices dropped sharply in 1892 but a low-cost process for leaching and precipitating copper from waste tailings saved the day for the company and paid off the mortgage.  As ore grades decreased, lower grade sulfide ores were successfully processed in a new concentrator built in 1895.  In 1906, the company built a large concentrator to process ore from its Humboldt Mine.  A new smelter was built south of Clifton in 1913.

Map of the Morenci and Metcalf Mining Areas, c1980, with Overlay of Old Mines and Railroads (Courtesy Phelps Dodge)
Another major producer in the area, the Detroit Copper Company, was formed in the 1870s to produce ore from mines near Joys Camp, later to become the first town of Morenci.  Initially, the mines only operated for a short time, but they were successfully reactivated.  By 1880, the company needed funding to build a smelter.  Phelps, Dodge, and Company of New York was approached for a loan.  In 1881, after an examination of the properties was made by Dr. James Douglas, the loan was granted and the smelter built south of Clifton.  In 1884, the smelter was moved to Morenci.  In 1886, the company constructed the first concentrator in Arizona.  The plunge in copper prices caused the operations to shut down in 1892.  When prices improved, another new concentrator was constructed in 1895.  It was unsuccessful at treating sulfide ores.  In 1897, Phelps, Dodge, and Company purchased the rest of Detroit Copper.  In 1900, the company built the Morenci Southern Railroad to connect Morenci to the Arizona and New Mexico Railroad at Guthrie.  The railroad operated until 1922.  In 1908, Phelps, Dodge, and Company became the Phelps Dodge Corporation with Dr. James Douglas as President.

Detroit Copper Company Smelter in foreground with Arizona Copper Company Concentrator under Construction in the Rear, 1906 (Courtesy Phelps Dodge)

The Shannon Copper Company Smelter in Clifton, 1902-1918 (Courtesy Phelps Dodge)
The third major producer in the area was the Shannon Copper Company, established in 1899.  Mining started north of Metcalf in 1901.  In 1902, its smelter started operation south of Clifton; however, the rich ores feeding the smelter were quickly exhausted and it shut down within the year.  A concentrator was built in Clifton in 1903 and the smelter resumed production.  The ore reserves at its mines were depleted by 1918.  With the collapse of the copper price in 1919, the company was sold to the Arizona Copper Company.

Labor strife shut down all of the companies in the district during 1915-1917.  Unfortunately, this was during a period of high copper prices.  The end of World War I brought the collapse of the copper price that affected all of the producers.  The underground mines in the Metcalf area, with the exception of the Coronado, shut down for good.


The mining and processing operations seen today reflect the many changes that have taken place at Morenci since Phelps Dodge gained control of the district in 1922.  During 1928-1930, an extensive exploration program revealed the large, low grade deposits now being mined.  By 1932, all underground mining had ceased.  In 1937, overburden stripping began for the Morenci Pit.  Power shovels loaded haul trucks.  Rail haulage of ore was introduced from the pit to a new concentrator built in 1942.  The pit continued to expand eventually necessitating the abandonment of the old Morenci town site.  The result was the new, modern town of Morenci located two miles away.

In 1953, an exploration program was begun in the Metcalf area.  The Metcalf Pit was started in 1969.  The Metcalf Concentrator was constructed in 1975.  The two pits merged in 1981 forming the huge pit area seen today.  In-pit crushers feed an extensive conveyor belt system that delivers ore to the concentrators.  In 1987, solvent extraction/electrowinning (SX/EW) production of pure cathode copper from dump leaching was started, marking the continuation of the legacy of leaching begun in the 1890s.  In 2007, Phelps Dodge became part of Freeport-McMoRan Copper and Gold.

Electric Locomotives Pull Ore Trains in the Morenci Pit, 1940s (Courtesy Phelps Dodge)




A Portion of the Huge Phelps-Dodge Morenci Open Pit Mine

Trucks Hauling Ore to the In-Pit Crusher

Blast Hole Drill (left) and Electric Shovels Loading Ore into the Haul Trucks (center)

MHAers Inspecting a Haulage Truck

MHAers Getting an Overview of the Morenci Pit and Leach Dumps

View of a Copper Leach Dump

The Solvent Extraction/ Electrowinning (SX/EW) Plant Recovers the Copper from the Leachate

Pure Copper Cathodes from the Refinery Tank House are Ready for Shipment



Photo Credits Johnny Johnsson


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