Tuesday, April 20, 2010

In the Pit

Mission Mine Pit, 2010 (Click to see larger)

By now you know I can be easily amused. So it shouldn’t be a surprise that when I saw a sign along the Arizona interstate highway advertising a mining museum, I pulled off to see what it was about.

We’re not talking West Virginia mining, the claustrophobic kind where guys go deep into the bowels of the earth and risk life and limb. Modern copper mining in Arizona is dangerous, but is at least conducted in an open pit in daylight, which means they start with a mountain or flat stretch of desert and just keep digging down until the amount of copper found in the soil is no longer profitable to extract.

I was first drawn to Asarco Corporation’s Mission Mine operation by an obviously man-made mountain range running parallel to I-10 south of Tucson. It goes for miles and is somewhere between three and four hundred feet tall. It’s so big that I’m sure someone would tell you it can be seen from outer space. You can tell it’s man-made because it’s so uniform in size and doesn’t have much vegetation on it yet. (And if that still isn’t enough to convince you, there’s also the fact that you can see heavy equipment up on top of the ridge increasing the height in forty feet increments.)

Asarco, the Mexican-controlled concern that owns the mine, must have a spotty environmental history. How could I tell? For starters, the film they show at the Visitor Center starts right off with a token message about environmental responsibility and never lets you forget that while they’ve been blowing up mountains and extracting millions of tons of copper ore over the years they’ve been leaving behind an environment so pure that a Sierra Club member would cry in amazement.

Hence the ersatz mountain range, built out of the crushed rock and earth (“tailings”) from which they’ve extracted copper, other marketable mineral byproducts and sulfuric acid.

The Mission Mine operation is located in a harsh climate that’s home to all kinds of nasty desert snakes. Just walking from the parking lot to the visitor center I saw scorpions, some kind of Sonoran version of prairie dogs, swarming bees and a rattlesnake.

I paid my $8.00 and joined a tour bus full of Midwestern retirees. I love tours like this because they’re almost always cheery PR anthems to industry. Likewise, the people who go on tours like this are almost always cornball patriots, big fans of industry and easily impressed by magnitude.

If you watch cable TV shows like Modern Marvels and Build It Big, you’d enjoy this tour. The metrics are impressive. The company owns 20,000 acres at this site. The open pit is six miles wide, a mile and a half across and 750 feet deep. (The far side of the pit seen in the photo above is several miles away.) Six times more earth has been extracted here than was excavated to create the Panama Canal. To move that earth from the mine to the mills they use trucks that can carry 375 tons at a time and have tires that cost more than some people’s houses. Two-thirds of the copper used in the U.S. comes from here. They expect to tap the last bit of it in thirteen years, after which the City of Tucson may acquire the site and use it as a landfill.

Prior to this tour, I didn’t know much about how copper is mined. But thanks to Roger, my Asarco tour guide, I’m now a “certified expert” in copper mining and milling and “visitor of the day” since I could correctly answer a question about how pure the copper is after the second milling. Knowledge I doubt I’ll ever have reason to use again.

But should you ever find yourself around a copper mill and wonder why things smell of pine oil, I’ll be able to tell you why. Or how an enzyme from soybeans is used as a copper binding agent. Not bad for a guy who barely made it through chemistry class, eh?

Lord knows, if I weren’t here to tell this kind of stuff, how would you know? And now you won’t even have to stay up late at night to watch the thirtieth rerun of Build it Big.

Mission Mine South Mill, 2010


  1. If I'd seen signs for that along the road, I'd have gone to see it, for sure. Thanks for the tour. That top photo looks like a man-made Grand Canyon. Amazing.

  2. There's a kind of horrible beauty to this pit.

  3. If this is off the beaten path, what is the path?