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Asarco Mining Operations in Arizona
Mission Mine, Tucson
Text edited by Rob Vugteveen, Director, Asarco Mineral Discovery Center


Mission Mine

The Asarco Mission Mine is about 15 miles south of Tucson, Arizona. It is 2 miles long, 1.75 miles wide and a quarter mile deep. The copper ore "contains" chalcopyrite (and not that much of it) is 0.67% copper, which means that 13 pounds of copper are produced from every ton of ore. In addition, about 3 tons of waste rock need to be removed to recover one ton of copper ore. Each year this mine produces 475,000 tons of concentrated copper ore (28% Cu), which eventually comes to 130,000 tons of pure copper metal, and 2 million ounces of silver.

Asarco mining link

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Mining Operations:
Almost on a daily basis one of the mine operations is to drill holes for blasting to loosen the rock for the shovels. The blasting is done with a mixture of ammonium nitrate and fuel oil (ANFO). As an aside, one blasting hole uses as much ANFO as was used in the Oklahoma City bombing.
The large shovels are powered by electricity, pictured in the above photos. Three scoops of ore or rock fill the very large trucks, which may hold 240 tons, four scoops for a 320-ton truck. The tires are 11 feet in diameter. As a side note, many of the trucks are driven by women.


Process to remove overburden soil and rock:

Text edited by Rob Vugteveen, Director, Asarco Mineral Discovery Center
Waste rock piles are unprocessed rock from all areas of the mine. Various rock types of different colors may be dumped in the same place, giving the waste rock piles a more mottled appearance as seen in this image labeled as "mine dump".
In fact, you can see that "dirt" in the first five benches at the bottom of the image (each bench is 40 feet tall, and you can scale the image that way). That light tan layer is the 200 to 250 feet of overburden that has to be removed to get to the rock. Depending on where you are in the pit, even that highest rock may or may not be mineralized, so it may also have to be removed to get to the ore-bearing rock. At Mission Mine, the ratio between all waste rock and ore is about 3-to-1. This ratio varies over the life of the mine and from mine to mine. The higher this "stripping ratio," the higher the operating cost of the mine. Those are the Catalina Mountains north of Tucson that appear in the background of the image.