MINING COPPER WITH HELP FROM FOUR-LEGGED FRIENDS

Technology, Know-HOW, and a Herd of Cows This Mining Tour Shows What It Takes to Get Copper Out of the Ground

The Asarco Mission Mine, an open-pit copper mine 15 miles south of Tucson, runs cattle - but not for beef or milk. The cows' story and the role they play in reducing the ecological impact of open-pit mining is just one fascinating bit of information offered during tours at the Asarco Mineral Discovery Center, a museum of sorts that provides an entertaining and educational look at copper mining in Arizona. The state is one of the largest producers of copper in the world, second only to Chile. The center's tours allow tantalizing glimpses into Asarco's mining and milling operation and the use of human-dwarfing machinery, high-tech computerized equipment, and old-fashioned know-how. While waiting for the tour buses that depart every 20 to 30 minutes, visitors meander through the center's exhibits to learn how copper forms in the Earth's crust, and how man removes it, purifies it, and uses it.

A wall display shows how magma molten rock rises, cools, and crystallizes, forcing superheated metal-laden water into surrounding rock to form mineral deposits.

Other exhibits demonstrate the milling, smelting, and refining processes. A film shown in the 35-seat theater lacking only popcorn and soft drinks offers more insight into the mining process and the widespread use of copper in everyday life. "Average Americans own more than 500 pounds of copper in their homes and vehicles," says Rob Vugteveen, director of the center. "Most often that use is in electrical wiring, appliances, plumbing fixtures, and pipes."

The tour bus first takes visitors to a viewpoint above the open pit, a quarter-mile-deep, two-milewide man-made mini Grand Canyon. There they see the slow-motion activity of huge electric shovels filling 320-ton-capacity trucks far below. Binocular telescopes bring the gargantuan earth movers close enough for viewers to appreciate their true size.

A little farther on, the tour bus I'm on stops while a truck carefully unloads 200 tons of ore into the seven-story-deep crusher at the Mission South Mill. The crusher reduces boulders up to five feet in diameter into manageable chunks the size of basketballs. A 10,000-gallon truck drives by, spraying water to control dust kicked up by the traffic.

"It's a rainstorm on wheels," says Vugteveen, chuckling. Asarco recycles about 80 percent of its water, losing this valuable resource only to evaporation and dust control.

At the entrance to the South Mill obser-vation deck, a droning noise and strong pine scent fill the air. Just outside the sound-proofed glass-walled gallery, two pairs of cylindrical grinding mills spin 24 hours a day reducing 20,000 tons of ore to a slurry. Yellow catwalks and staircases crisscross the room like a child's erector set. Small pieces of ore that are still too large for the next step sit on a conveyer belt that takes them back to the mills. The whole process consumes about a pound of five-inch-diameter steels balls for each ton of rock milled.

The next step goes on nearby where huge vats of frothing foam shimmer with the green-brown metallic sheen of a drag-on's skin. The slurry of powdered rock and water is mixed with lime, pine oil, and a special collector reagent. Like a child blowing bubbles into chocolate milk, flota-tion machines whirl air into the concoc-tion. The collector binds with the copper minerals and sticks to the air bubbles, then floats to the top and wafts over the side of the tank, while the remaining mineral-stripped material sinks to the bottom. This flotation process was discovered, visitors are told, when a woman (scrubbing her miner husband's dirty clothes) noticed mineral flecks clinging to pine-oil soap bubbles.

The final process here removes the water through a rotating cloth filter, leaving a fine powder containing 28 percent copper. This “copper concentrate” may go to the Asarco smelter in Hayden, where it is made into 99.99 percent pure copper. Then it goes to the Asarco Copper Refinery in Amarillo, Texas.

The most obvious thing that many people notice about mines are the tailings dams, where all that ground rock ends up. Left alone, this material could take decades to recover enough to support life. That's where the cows come in.

The tour guides point out that Asarco's use of up to 100 head of cattle, affectionately christened the ASARCows, leads to a much quicker reclamation. The ASARCows feed on hay spread on the tailings, their hooves till the hay and their own naturally produced organic fertilizer drops into the powdered rock to create a sustainable soil. What Mother Nature might take decades to do, Asarco with a little help from its four-legged friends does in less than five years: help bring back the grasses, native trees, and shrubs.

Rob Vugteveen surveys the reclaimed desert land and the Mineral Discovery Center from atop a nearby hill as a bus filled with schoolchildren returns from their mine tour.

“I hope 20 to 25 years from now somebody who went on this tour as a kid will see something here as a solution to some future problem,” he says.

You have to wonder, I think, if it will in-volve cows.

While on the mine tour, Phoenix-based Theresa Williams reminisced about her Norwegian mining heritage and couldn't wait to get home to polish her copper. David H. Smith was amazed by the amount of ore taken out of the pit and how little copper it yielded.

WHEN YOU GO

The Asarco Mineral Discovery Center, 1421 W. Pima Mine Road, Inear Sahuarita, is open year round except major holidays frond 9 A.M. to 5 P.M., Tuesday through Saturday. Admission is free; tickets for the mine and mill tour cost $6, adults; $5, seniors; $4, ages five-12; free, under five. The tour and the discovery center are wheelchair-accessible. There's a gift shop on-site.

To reach the center from Phoenix, travel east and then south on Interstate 10 through Tucson and take the Interstate 19 exit toward Nogales. Follow 1-19 to Exit 80, Pima Mine Road, and turn west. The center's main entrance is on the south side of the road. For more information, see the center's website at www.mineraldiscovery.com or call (520) 625-7513; for reservations for groups of eight or more, call (520) 625-8233.