The growing renewable energy industry is helping to add a new sheen to Colorado’s silver-mining industry, creating a paradox for environmentalists. There is newfound optimism in the hills above Idaho Springs, where brown piles of mine tailings surround hundreds of long-abandoned mines, 9News reports. The solar energy industry needs silver, says miner Al Mosch, who is reopening the Poor Man Mine.

Silver futures are rising, up 27 percent in May alone, to hit $15.60 an ounce–the largest monthly gain since 1983, according to The Denver Post. Of course, mining brings environmental concerns. In Summit County, for instance, officials are seeking to minimize the impact of cyanide heap-leaching, according to Summit Daily News.