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, foundry sand, and iron ore pelletizing. Common clay and shale contain mixtures of differing proportions of clay, including illite, chlorite, kaolinite, and montmorillonite, plus other nonclay materials. The largest user of these clays is the structural clay products industry, which manufactures brick, drain tile, sewer pipe, conduit tile, glazed tile, and terra cotta. Fire clays can withstand very high temperatures and consist mainly of kaolinite. These clays are used in commercial refractory products such as firebrick and block. Fuller's earth, either the attapulgitetype or montmorillonite-type, is used in pet waste absorbents, oil and grease absorbents, and pesticide carriers. Kaolin has many industrial applications because it has good covering or hiding power when used as a pigment, is soft and nonabrasive, has low conductivity of heat and electricity, and is inexpensive. Major domestic uses for kaolin in 1992 were paper coating, paper filling, fiberglass, paint, rubber, brick, and portland cement.

The focus of this paper will primarily be placed on ball clay which is used for the production of ceramic floor and wall tile for home and industrial uses. The manufacture of clay products involves the conditioning of basic clay ores by a series of processes. These include separation and concentration of clay minerals by screening, floating, wet and dry grinding, and blending of desired ore varieties; followed by forming; cutting or shaping; drying or curing; and firing of the final product. The Stone, Clay, Glass and Concrete Industry is quickly growing industry and with any emergent industry, especially production industries, the need for pollution control increases along with growth.

The following regulations apply to the Stone, Clay, Glass and Cement Industry: RCRA (Resource Conservation and Recovery Act), CERCLA (Comprehensive Environmental Response Compensation and Liability Act, EPCRA (Emergency Planning and Community Right-to-know Act, CWA (Clean Water Act), CAA (Clean Air Act), and TSCA (Toxic