When Dennis Fischer started talking about more possible deposits of copper at Rosemont, my ears perked up.

Maybe there was some way I could support this mine after all.

Over the years, the proposed Rosemont Mine has become the most polarizing issue in Tucson. It seems few of us have remained in the middle, struggling as I have with contradictory desires for the burst of job creation promised by Rosemont on one hand and for preserving precious nearby wild places on the other.

Fischer, Rosemont’s project site coordinator, led the tour I took earlier this month of the proposed mine site, about 30 miles southeast of Tucson in the northern Santa Rita Mountains. I wanted to see the site and look for a way to overcome my own main objection to the mine — its short productive life — which is different from most objections I hear.

My reasoning has long gone like this: I can accept some environmental destruction if the economic benefits are big enough and the destruction is mitigated. Rosemont has clearly worked to reduce the effects of what is an inherently destructive economic activity — otherwise the project likely would have been roundly rejected by locals long ago.

But my other concern has stuck with me since the years when I was business editor at the Star and the reality dawned on us that this new Canadian company, Augusta Resource, was serious about trying to mine in the Santa Ritas.

The present estimate is that, if permits are issued, construction of the planned Rosemont pit will take about two years, followed by about 21 years of mining, then three years of winding down operations. Total: 26 years.

Then, as far as we can see now, it’s over. What’s left is a pit more than a mile across, partially on National Forest land, slowly filling with water, and hundreds of acres of tailings, that the company will “reclaim” during the mining process and thereafter.

None of the workers would get a full career out of this mine, and who knows what their job prospects will be afterward.

Despite the fact that copper is a notoriously cyclical industry, with its attendant layoffs and hiring sprees, most of Arizona’s open pits in operation now have existed and employed miners for generations. Morenci started in 1937, Bagdad in 1945, Ray in 1948, Sierrita in 1957 and Mission in 1959.

Some would argue Rosemont’s short projected life is a good thing: The destruction would be short-lived and the reclamation, aside from the pit, would be quickly done. But I view it as bad: The economic benefit will be short-lived while the environmental destruction remains at a large scale.

That’s why Fischer’s reference to the possible deposit at Broadtop Butte, just north of the Rosemont pit site, tempted me. Maybe another deposit would mean longer-term mining, a bigger economic benefit, and a better justification for the damage to what is a beautiful oak woodland, in a broader area where I’ve hiked several times.

But Fischer and, later, Rosemont CEO Rod Pace, told me that there’s nothing definite beyond the main pit Rosemont has planned to dig. The deposit at Broadtop would likely require underground mining, Pace said, and that would mean the copper ore would have to exist at a higher concentration to make mining there economically feasible. So it’s unclear if any mining will ever occur there.

To me, that’s a bad thing, but to Gayle Hartmann, of Save the Scenic Santa Ritas, it’s a good thing.

“The current proposition is a tragedy, but that one would be even more so,” she said.

Many arguments have been made for Rosemont — that we need copper, that copper is important to the “green” economy, that the government should not interfere with private business — but I find these severely lacking.

Copper is a global commodity, available on the open market, that we produce a lot of in Arizona, where there are existing pits that could be reopened for mining if the need arose. We may need copper, and copper may be crucial to the green economy, but we don’t particularly need this copper at the Rosemont site, which would wind up on the open market anyway. Also, this is not a situation where the government could or should step aside: Much of the proposed mine’s operations are located on public land.

For me, the only salient argument for Rosemont is jobs — good blue-collar jobs for people without a college education — something we are short of in the Tucson area. Manny Armenta, a longtime leader of union miners affiliated with the United Steelworkers, pointed out their value.

“These are livable-wage jobs we’re talking about. These are jobs where someone can support their families,” Armenta told me Thursday.

He’s right, of course. The 450 projected mining jobs would be a huge boost to those who get them and would have a positive ripple effect in the local economy.

However, the idea that this is the Tucson area’s big opportunity of the future is, for me, overblown.

To get a better perspective, I asked George Hammond, an economist at the UA Eller College of Management’s Economic and Business Research Center, about mining’s place in the Tucson area’s economy. It turns out that while, historically, mining was the foundation of Southern Arizona’s economy, that’s not been the case lately.

The 2,000-odd jobs in mining in Pima County in 2012 amounted to 0.6 percent of our area’s 361,000 total jobs, Hammond said. If you add Rosemont’s projected 450 jobs to that, you bring mining’s proportion of our workforce up to 0.7 percent.

With its high productivity, the industry has an outsized impact, though. In 2012, mining made up 2.7 percent of our local gross domestic product, Hammond said.

Those figures are much higher for outlying copper-mining communities in Pinal, Graham and Greenlee counties, of course. But this mine would probably draw most of its labor force from the Tucson area, where other job opportunities exist, if in unsatisfactory numbers.

Whether or not this mine is ever built, Tucson’s challenge remains creating those other opportunities. If it is built, only a relatively few members of the local workforce would work there, and, with the mine’s short lifespan, most of them would need new jobs after it closes.

For me, that’s not enough benefit to justify the environmental damage.

Contact columnist Tim Steller at tsteller@azstarnet.com or 807-7789. On Twitter: @senyorreporter