The Morenci copper mine operation in southeastern Arizona

Copper Mining in Southeastern Arizona at the Morenci Operation

The Morenci Operation: Arizona

Copper is a metal that is typically found in ore form. It is smelted or leached out of the ore and used in myriad different applications. Copper wire and bus bar are used in electrical applications while jewelers, home builders, and even aerospace engineers have valued its high conductivity, relative beauty, and fairly low cost for decades. The Spanish came to appreciate the value of copper hundreds of years ago as they mined it using very similar techniques as are used today.

Arizona has been home to copper mines for centuries. The first copper mines in the area were under Spanish rule in the 1750's, and Arizona has become one of the world's largest copper sources. The Morenci mine, located in a desolate area approximately 150 miles southwest of Phoenix is the largest operational mine in the state, producing over 247 million tons of ore per year. This ore is processed on site and yields approximately 15,000 tons of copper and over 355,000 tons of copper cathode. The copper ore is placed on leach pads on site; so much of the leaching and mineral separation is done immediately after the ore is mined. This helps cut down on production costs.

History of the Morenci Mine

The Detroit Copper Company started mining at Morenci in 1872. Copper Queen Consolidated Mining later bought out the operation in 1885, and the company name was officially changed to Phelps Dodge in 1917. In modern times, Phelps Dodge has merged with Freeport McMoRan Copper & Gold, whose principal claim to fame is the Grasberg copper and gold mining operation in Indonesia. Morenci is currently the largest copper producing mine in North America and continues to be a major boon to the Phelps' Company copper output. This output is second only to that of Chile's Codelco Company. Phelps Dodge Morenci, Inc. was established in 1986 as a partnership between Phelps Dodge Mining Company and Sumitomo Metal Mining Arizona Inc.

The copper-bearing mountainous region in southeastern Arizona was first identified by Americans in 1865. A regiment of California Volunteers showed that the future site of the Morenci mining operation was part of a vast porphyry copper orebody extending across a dissected mountain terrain. Essentially, it was a small part or finger of a huge copper ore vein contained in the mountains near Silver City, Arizona. Besides copper ores there are many other types of mineral and metals in this deposit including sulphide and oxide ores; pyrite and chalcocite being the main sulphide minerals, and chrysocolla and malachite the predominant oxides. Molybdenite, galena and sphalerite are also present nearby.

Environmental Concerns and Impacts

The process of ore extraction by smelting is quite environmentally damaging. Many of the largest copper mines in the state of Arizona are designated as Superfund Clean-up Sites, or places where the Federal Government has placed restrictions on future operations while mandating clean-up of environmental toxins and contaminants. While the Morenci mine itself no longer has a smelter, one of the mine's most utilized smelters, called the Miami smelter, is currently on the Federal Government's list of Superfund sites due to toxic metals and contaminants that have leached through into the groundwater nearby.

The hydrometallurgical process of leaching copper ore also has many environmental concerns. This process often involves radioactive chemicals and other toxic chemicals. The Philips Dodge operations are regular recipients of Notices of Violation from the U.S. Attorney General. These notices reflect violations to environmental or other previously outlined health concerns associated with the mining operation. Some other major environmental concerns for this company, including the Morenci location are:

1) Phelps Dodge has pending water quality permits intended to stop the discharge of mining toxic waste into groundwater used for public and private drinking water.

2) Phelps Dodge has state and federal superfund and compliance programs now in place or pending.

3) Phelps Dodge has extensive environmental and reclamation costs at present and in the future.

These and other concerns come with mandatory permitting and regulation from the Federal Government. They have cost the Philips Dodge Company over $822 million dollars from the years 2002-2005 alone. But no amount of money can make up for the fact that million of gallons and thousands of tons of these toxic substances have been contaminating the area around the Morenci site for decades. It is extremely costly and time-consuming to remove these substances, which if left untouched, will remain in the soil and groundwater of the region for millions of years. The smelting operations in the early years of the mine's operation were much more environmentally harmful than those of later periods, and the Federal Government did not start regulating polluters until a few short decades ago.

The State of Arizona has also come down hard on the Philips Dodge Company for destroying migratory bird habitat and breeding grounds at the Morenci site as well as other sites across the state. The State of Arizona has mandated that the company pay millions in clean up and rehabilitation fees for these habitats. The Morenci mine currently estimates that it has over 250 million tons of copper ore in reserves and will likely operate for years to come. The region's resource-rich mountains and desert area make it one of the most profitable in the world.