A potential mine in the Blackfoot watershed?
Near the old mining ghost town of Garnet, at the headwaters of Union Creek above the lush, rural Potomac valley, there’s an outcrop of rock stained iridescent blue and green with copper minerals. That colorful cliff has inspired numerous attempts to see if there’s “ore” where that rock came from, and the most recent explorer is Kennecott Exploration Company, a wholly owned subsidiary of the multinational Rio Tinto Group. They’ve been sporadically investigating this area since 2005. At a meeting in the Potomac Community Center on May 31st, 2012, a representative from Kennecott’s Salt Lake City office outlined the work they are undertaking in the area this summer – a magneto-telluric survey to try to define the sub-surface extent of the ore body. This passive geophysical survey follows a drilling program that completed 7- 8 boreholes in 2007 and 2008 and reportedly showed “mixed” results. The Kennecott spokesperson was quick to emphasize that they are still very early in the exploration process, and that the company doesn’t know if they have a deposit that would ever be economically feasible to mine or not. Only 1% of the targets they ever investigate become a mine.
Perhaps the most interesting bit of information from this meeting was that the ore they believe they are looking at is a “porphyry copper” deposit – a disseminated, vein-rich type of deposit that often hosts gold and molybdenum along with copper. Porphyry copper deposits host some of the largest mines in the world and more often than not, they are open pit mines (Butte and Bingham Canyon in Utah are examples). In this case, Kennecott was quick to note that this deposit is not “surface-mineable” because the top of the mineralization is 1,800 feet below the surface. But any type of mine would still require land (and water) for mineral processing and tailings disposal. The end result would be an ore concentrate that would be shipped out of the valley by truck, probably to the nearest rail line.
Although it’s much too early to speculate on the environmental consequences of a mine here, we are concerned, and we are tracking the project carefully. We appreciate Kennecott’s willingness to talk to the public this early in the exploration phase – and they promised they’d hold another meeting in the fall when results from the geophysical survey are in. Stay tuned.