Sone Clay and Glass Industry
The Stone, Clay, Glass, and Concrete Products Industry generates a broad array of products, primarily through physical modification of mined materials. The industry includes establishments engaged in the manufacturing of flat glass and other glass products, cement, structural clay products, pottery, concrete and gypsum products, cut stone, abrasive and asbestos products, and other products. Under the Stone, Clay, Glass, and Concrete is the Structural Clay industry which will be the primary focus of the report. Clay consists of the finest-grain particles in sediment, soil, or rock, and a rock or a deposit containing a large component of clay-size material. Clay can be composed of any inorganic materials, such as clay minerals, allophane, quartz, feldspar, zeolites, and iron hydroxides, that possess a sufficiently fine grain size. Along with organic matter, water, and air, clays are one of the four main components of soil. Physical properties of clay include plasticity when wet, the ability to form colloidal suspensions when dispersed in water, and the tendency to clump together (flocculate) and settle out in saline water. Establishments that fall within the Structural Clay Products Industry (SIC code 325) are primarily engaged in using different types of clay and other additives to manufacture brick and structural clay tile, ceramic wall and floor tile, clay firebrick and other heat-resisting products, and clay sewer pipe. The mining of clay used to make structural clay products are not included within SIC code 32. The U.S. Bureau of Mines categorizes clay into six groups: ball clay; bentonite; common clay and shale; fire clay; fuller's earth; and kaolin. Ball clay is a plastic, white-firing clay that has a high degree of strength as well as plasticity. Principal ball clay markets in 1992 were pottery, floor and wall tile, and sanitary ware. Bentonite is a clay composed mainly of smectite minerals. The three major uses of bentonite in 1992 were drilling mud,