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ROCHESTER MINE Rochester Reloads A U.S. silver mine processes valuable leftovers from its 27 years of operation to boost productivity—and profitability By Russell A. Carter, Managing Editor Although reserves are sufficient to keep its in-pit production going for many more years, Coeur Mining's Rochester silver mine also has begun processing an estimated 150 million tons of waste material that contains valuable silver content. (Photo courtesy of Battle Born Engineering) It's been a busy year for Coeur Mining's Rochester operation. The long-running silver/gold surface mine, located near the town of Lovelock in western Nevada, has begun exploiting a new source of mineral revenue for its Chicago-based parent company. And, a recent announcement that its proven and probable silver reserves increased more than 91% this year—along with an 96.4% increase in gold reserves— offers increased clarity about its role in Coeur's future plans. Rochester is Coeur's oldest mine and was once the company's largest producer— but the Palmarejo underground/open-pit operation in Mexico now holds that distinction. However, Coeur Mining Inc. President and CEO Mitchell J. Krebs believes that Rochester has the potential to become one of the company's largest cashflow generators in the next five years, and Coeur has indicated that later this year it plans to release an announcement related to further expansion at the mine. It's a very different picture from the darker days of January 2008, when Coeur—then known as Coeur d'Alene Mines 64 E&MJ; • NOVEMBER 2013 Corp., based in its namesake northern Idaho city—announced that it was looking at "strategic alternatives" for Rochester. But the company reconsidered five months later and retained ownership of the mine, which at the time had measured and indicated mineral resources of more than 27.8 million oz of silver and 180,000 oz of gold. In contrast, Coeur just reported that as of mid-September, the Rochester property contains approximately 69.3 million silver oz and 560,000 gold oz contained in measured and indicated resources, and about 26.2 million silver oz and 105,000 gold oz from inferred resources. Those recent figures, according to the company, don't reflect the results of its 2013 drilling at Rochester, an ongoing program that has been under way since 2012 to delineate the characteristics of its newest source of mineralization—the huge piles of mining waste, sometimes called non-ore rock, that have accumulated since the mine began operating in 1986. The stockpiles, covering about 40 acres, are expected to play a steadily increasing role in Rochester's future production plans, according to Coeur Rochester General Manager Robert Stepper. "The mine opened in 1986 and the first (Stage I) pad was completely full by about 1991. At the time, it was loaded with ore grading about 2.5 oz per ton silver, with a 1.5 oz per ton cutoff," he explained. Anything below that cutoff went to the waste stockpiles. "Although there is some true waste in the waste stockpiles from those years, there's also plenty of material that averages between 0.8 and 0.87 oz per ton. We're very interested in that," he said. Over the next few years, Rochester will focus on three major stockpiles that comprise about 100 million tons of material in total; most of this material has been drilled and assayed under the current program, but as much as 50 million more tons remain in two other stockpiles, and the company expects that drilling results from this additional material will allow Rochester to expand its reserve base even further. As with the previously drilled stockpile material, the remainder will be drilled using reverse-circulation rigs, on 50-ft (15-m) centers. Coeur just completed a $5 million upgrade to the mine's primary crusher and plans to spend another $22.5 million to expand Rochester's heap leach capacity. Recent modifications to its Merrill-Crowe plant have doubled that facility's processing capacity, and a cost-cutting program involving a number of areas, ranging from lower reagent and power consumption to shortened haul distances, represent ongoing efforts to control the mine's operating costs. Quite possibly the most formidable obstacle standing in the way of its future success was removed in late June when Coeur announced it had reached an out-ofcourt settlement with Rye Patch Gold U.S. Inc., a Vancouver, B.C.-based exploration company, ending a dispute over ownership of mining claims covering 7,500 acres that impinged upon Rochester's active mining areas. The settlement called for Coeur to pay Rye Patch Gold $10 million in cash plus a 3.4% net smelter royalty covering 39.4 million silver equivalent oz of net metal sales. In exchange, Rye Patch transwww.e-mj.com