The Wisconsin Industrial Sand Co.'s Maiden Rock facility stands in Maiden Rock, Wisconsin, U.S., on Thursday, Aug. 15, 2013. The 1,696 acre mine is one of only four underground industrial sand mines in the country. Because of the size and strength of the silica sand mined at this location, the industrial sand from this facility is used primarily in hydraulic fracturing operations in the oil and gas industry. Photographer: Ariana Lindquist/Bloomberg via Getty Images