A stockpile of sand at the Superior Silica Sands facility in Barron, Wis., in 2015. The market for sand—a key ingredient in fracking—is surging once again as U.S. oil production rebounds, and the rising price of the tiny grains threatens to cut into energy companies’ profits. Now that crude oil is selling for just less than $50 a barrel, American shale companies have rushed back into the oil patch , and they are using more sand to help supersize their wells. Sand props open underground fissures, which allows oil and gas to escape to the surface. But the millions of pounds of sand being poured down wells is pushing up sand prices, eroding some of the profits that energy companies have managed to regain since the oil bust ended. Some are concerned sand supplies, diminished during a two-year oil-price downturn, could stall the drilling renaissance. “Companies are worried about […]