Morenci Mine

Description: Morenci is an open-pit copper mining complex that has been in continuous operation since 1939 and previously was mined through underground workings.

Did you know? We have expanded our mining and milling capacity at Morenci to process additional sulfide ore identified through exploratory drilling. The project targets average incremental annual copper production of approximately 225 million pounds through increases in milling rates to 115,000 metric tons per day (mtd). 

Location: Greenlee County, Arizona, approximately 50 miles northeast of Safford on U.S. Highway 191.

Ores: The Morenci mine is a porphyry copper deposit that has oxide, secondary sulfide and primary sulfide mineralization. The predominant oxide copper mineral is chrysocolla. Chalcocite is the most important secondary copper sulfide mineral, with chalcopyrite as the dominant primary copper sulfide.

Processes and facilities: The Morenci operation consists of two concentrators capable of milling 115,000 mtd, which produce copper and molybdenum concentrate; a 68,000 mtd crushed-ore leach pad and stacking system; a low-grade run-of-mine (ROM) leaching system; four solution extract (SX) plants; and three electrowinning (EW) tank houses that produce copper cathode. Total EW tank house capacity is approximately 900 million pounds of copper per year. During second quarter of 2015, Morenci’s concentrate leach, direct-electrowinning facility (which was placed on care-and maintenance status in early 2009) resumed operation.

Background: Phelps Dodge & Company invested $50,000 in the property in 1881, marking the New York mercantile’s first venture into mining. Through acquisition, Phelps Dodge & Company consolidated all mining operations in the district by 1921. Initially underground, Morenci transitioned to open-pit mining beginning in 1937. The operation nearly doubled its production capacity during World War II at the urging of the U.S. government to meet wartime needs. Morenci’s first SX/EW plant was commissioned in 1987. Once home to two smelters, the last smelter ceased operation in 1984. Both have been demolished and reclaimed.

Ownership: 72% (undivided interest) FCX; 28% affiliates of Sumitomo Corporation.