Morenci Mine

Useful Information

Location:	80 km northeast of Safford. Morenci, Greenlee County, eastern Arizona.
Open:	All year Fri, Sat 9, 13. Reservations required. [2008]
Fee:	Adults USD 8. [2008]
Classification:	Copper Mine Biggest Open Cast Mine
Light:	Incandescent
Dimension:	P=380,000 tons/a copper, 500 tons/a molybdenum. L=5,200 m, W=4,800 m, D=400 m.
Guided tours:	D=2.5 h.
Photography:
Accessibility:
Bibliography:
Address:	Morenci Mine, 4521 US Highway 191, PO Box 187, Morenci, AZ, 85540, Tel: +1-928-865-4521, Fax: +1-928-865-4822. Morenci Mine Tour, Tel: +1-877-646-8687. Graham County Chamber of Commerce, Tel: 888-837-1841.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then. Please check rates and details directly with the companies in question if you need more recent info.

History

1872	Morenci opened as an underground mine.
1881	Phelps Dodge & Company invested $50,000 in the mine.
1921	Phelps Dodge owned all mining operations in the district.
1937	transitioned to open-pit mining.
1983	Arizona Copper Mine Strike.
1984	smelter operation ended.
1987	first SX/EW plant commissioned.
2001	concentrator shut down.
2007	merger with Freeport-McMoRan Copper & Gold.

Geology

At Morenci a low grade porphyry copper ore is mined. Actually it is a combination of chrysocolla, chalcopyrite, and chalcocite. Chrysocolla is a oxide copper mineral, while chalcocite and chalcopyrite are copper sulfides. By-products of the mine are silver, gold and molybdenum.

The copper is extracted with the SX-EW process, which makes it possible to extract copper from low-grade sulfides. SX means solution extraction, the copper is leached from the surrounding rock, the solution is concentrated and then collected from the solution by electrowinning (EW), the process of collecting ions at a cathode with an electric tension. The specialty of Morency mine is the Concentrate Leaching Project which started in 2007. The company has developed a proprietary medium-temperature, pressure-leaching and direct-electrowinning technology. This process is optimized for the local ores and will optimize the process and reduce costs by eliminating the concentration of the solution step.

Description

Postcard of Morenci, Arizona, circa 1910.

Morenci Mine is one of the biggest open cast mines of the world, several kilometers long and wide, and several hundred meters deep. It is said to be the largest copper mine in North America. The company which operates it, Freeport-McMoRan Copper & Gold Inc is the worlds largest publicly traded copper company.

The enormous field of open casts, five huge holes of which three are currently worked, is located along Clifton Alpine Highway (Hwy 191) north of Morenci. So it is pretty easy to see the open cast just by driving through, and there are numerous good lookouts. There is one prominent lookout which was prepared for the visitors with a platform and some informative signs. It is located 8 km north of Morenci at Hwy 191.

Additionally there is a two and a half hour bus tour through the mine provided by the mining company. The tours start at the Morenci Motel, where an introduction is given on safte on the tour, the itinerary and some mining technology. The tour is done by coach, but there are many stop including lookouts, the opwn cast, and various processing plants. This is a working mine, not a museum, so all machinery is in operation.