It's not exactly the Grand Canyon, but your next Arizona vacation could include the enormous crater of an open-pit copper mine. ASARCO Inc. ow offers bus tours of its Mission Mine near Tucson, hauling visitors to an overlook of the two-mile-long, 13'4-mile-wide hole deep enough to hide a 100-story building. Tourists can also see "the concentrator," a facility that produces 130,000 tons of copper concentrate each year. John Low, mine manager, says most people don't realize how much they rely on copper, from the 50 pounds of wiring in a car to the few hundred pounds of plumbing and wiring in a house. It takes a ton of crushed earth to produce 13 pounds of copper. The new visitors' center fails to mention the company's status as the number-one polluter in Arizona and the sixth major industrial polluter in the nation (HCN, 9/16/96). Instead, it pictures land-reclamation techniques such as grazing cattle on straw-covered tailings piles. For more information contact Rob Vugteveen, director of the visitors' center, at 520/625-7513.