U.S. Silica Holdings, Inc. produces and sells various commercial silica and industrial mineral products. The company offers whole grain commercial silica products to be used as fracturing sand in connection with oil and natural gas recovery; the manufacturers of architectural and solar glass; and foundry and building products industry. It also provides ground commercial silica products for use in plastics, rubber, polishes, cleansers, paints, ceramic frits and glazes, textile fiberglass, and precision castings; and fine ground silica for use in premium paints, specialty coatings, sealants, silicone rubber, and epoxies. In addition, the company offers certain other industrial mineral products, such as aplite, a mineral used to produce container glass and insulation fiberglass, and is a source of alumina to form defects in glass; calcined kaolin clay, a mineral primarily used as a functional extender in paints, plastics, specialty coatings, and rubber; and magnesium silicate, as well as produce and sells an adsorbent made from a mixture of silica and magnesium for preparative and analytical chromatography applications. It serves oil and gas recovery, glass, building products, foundry products, chemicals, and fillers and extenders markets. As of December 31, 2011, it had approximately 316 million tons of estimated proven and probable recoverable mineral reserves. The company was formerly known as GGC USS Holdings, Inc. and changed its name to U.S. Silica Holdings, Inc. in July 2011. The company is headquartered in Frederick, Maryland. U.S. Silica Holdings, Inc. is a subsidiary of GGC USS Holdings, LLC.