U.S. Silica Holdings Inc. is a producer of industrial minerals. The Company produces sand proppants, whole grain silica, ground silica, fine ground silica, calcined kaolin clay and aplite clay. The Company is a domestic producer of commercial silica. The Company operates in two segments based on end markets served: Oil & Gas Proppants, and Industrial & Specialty Products. The Company operates as a research and development specialist for customized products and solutions utilizing the same raw materials. The Company serves the industries including oil and gas, glass, chemicals, foundry, building products, fillers and extenders, recreation, industrial filtration and treatment, and testing and analysis. As of February 26, 2014, the Company operates 15 production facilities across the United States and controls 297 million tons of reserves, including approximately 138 million tons of reserves that can be processed to meet the American Petroleum Institute frac sand size specifications.