This category covers establishments primarily engaged in mining, milling, or otherwise preparing kaolin or ball clay, including china clay, paper clay, and slip clay. Establishments primarily engaged in grinding, pulverizing, or otherwise treating clay, ceramic, and refractory minerals not in conjunction with mining or quarrying operations are classified in SIC 3295: Minerals and Earths, Ground or Otherwise Treated.
212324 (Kaolin and Ball Clay Mining)
In the early 2000s, a total of 28 U.S. firms operating 124 mines produced 9.13 million metric tons of kaolin and ball clay. Of the total U.S. production of clay and shale in 2003, which reached 39.3 million metric tons with a value of $1.6 billion, kaolin accounted for about 20 percent. Ten states, led by Georgia, produced kaolin in the early 2000s. Kaolin's primary uses are for paper coating and filling (54 percent), refractories (17 percent), and other uses (29 percent).
The ball clay segment of the industry was rather small and consisted of four companies in four states in 2002. Tennessee was the leading supplier of ball clay, producing 59 percent of total U.S. output. Following Tennessee were Texas, Kentucky, and Mississippi. U.S. production of ball clay in 2002 reached 1.12 million metric tons with an approximate value of $47 million. The major ball clay markets in the United States were floor and wall tile (41 percent), sanitary ware (25 percent), and other uses (34 percent).
Clays are classified according to their relative plasticity or malleability, their strength when moist (green strength), their strength after drying (dry strength), their air shrinkage properties, and their vitrification range. Vitrification refers to the process by which clay molecules begin to fuse when exposed to heat. A clay's vitrification range therefore describes the temperature levels between which the clay begins to fuse and when it achieves its final fusion or hardness.
Clays are often mixed or blended to achieve the desired properties dictated by their end use. Thus, whiteware ceramic consists of kaolin, ball clay, feldspar, and ground silica. Kaolin, or china clay, derived its name from the hill where it was first extracted in Kao-Ling, China. Historically, more than half the annual U.S. production of kaolin was used as filler and coating material in high-quality paper. Along with wood pulp, kaolin traditionally constituted a large percentage of the paper's content. The properties that recommend kaolin as a paper clay include natural brightness, ink absorption characteristics, chemical inertness, and superior dispersability when introduced into the water solutions from which the final paper mixture is derived.
There are no commercial substitutes for kaolin as an ingredient in coated paper. The increasing scarcity of wood pulp and the high costs of transporting kaolin outside the southeastern United States however, spurred the papermaking industry to develop alternatives to kaolin as a paper filler in the 1980s. The invention of lime-and calcium carbonate-based alkaline paper manufacturing techniques meant that papermakers would require less wood pulp for paper production. It also meant that they could avoid the high transportation costs associated with kaolin paper fillers—resulting in a potentially long-term loss of demand for the industry's kaolin mining firms.
However, in addition to its uses in papermaking, kaolin is also favored as a filler in rubber production for its low cost and stiffening or reinforcing characteristics, as well as for the properties that recommended it in papermaking. Comparatively smaller amounts of kaolin have been used as extenders and fillers in the manufacture of paint, linoleum, leather, wallpaper, textiles, and fertilizers. Other uses of kaolin include the production of fungicides and insecticides and the manufacturing of porcelain, chinaware, and other ceramic products. Highly refined kaolin has also been used in cosmetics and pharmaceutical products.
Although kaolin as a commodity is relatively inexpensive, it is less common than other clays and therefore has a higher unit price compared to them. Because kaolin has a low per ton price compared to other nonclay commodities, it yields its producers only slim profit margins—unless it could be extracted and processed in greater bulk without added cost or offered to the market in a refined, higher-priced form. For example, in the late 1980s, Georgia-based Nord Kaolin Company introduced a line of customized kaolin-based pigments to act as "opacifiers" to reduce the transparency of paper and to augment the printing quality and whiteness of premium or "glossy" magazine paper, lightweight periodicals paper, and uncoated copier paper. The firm sold more than 12,000 tons of such kaolin-based pigment paper products in 1992.
Historically, about 90 percent of U.S. kaolin production came from mines in Georgia and South Carolina, but North Carolina provided another source of workable deposits. The United States and Great Britain historically led world production of kaolin. In the late 1960s, the kaolin production by Germany, India, and France combined amounted to less than one-third the kaolin production of Great Britain alone.
Ball clay, a light-burning, high-grade ceramic clay, derived its name from the shape it took when it was removed from open pit mines in the early days of the clay mining industry in Great Britain. More than 89 percent of U.S. ball clay originated in western Tennessee and Kentucky, but other mined deposits existed in California, Maryland, Mississippi, and New Jersey. Ball clays differ in color, plasticity, strength, and firing properties, but almost all their uses are ceramic. High-grade ball clay is used in the manufacture of dinnerware, porcelain, and ceramic-based bathroom fixtures. Ball clay is also used to produce "wad" and "sagger" clays used in ceramic kilns to protect and support the clay being baked. Ball clay is shipped in bags and bulk carload lots—in ground, "air floated," lump, or shredded form. Like kaolin, ball clays are produced in relatively small quantities compared to other clays and thus have a generally higher unit price.
Kaolin and ball clays were most often mined by directing hydraulic high-pressure jets of water on the clay faces of open pits, loosening the soft clay from the deposit. The liquefied clay mixture or "slip" was then raised by bucket elevator to a flume or chute that transported it to the preparation plant. In other methods, the clay was mined by removing the overburden (or overlay of soil or rock) by power shovel or dredging "dragline" machine. The exposed clay was then mined by a power shovel and delivered to the preparation plant by conveyer belt, truck, or rail.
At the preparation plant, the clay mixture was refined and "de-watered" by mechanical drying equipment and filter presses. The undesired grit minerals (such as sand, rutile, or mica) were separated from the clay by such processes as grinding, washing, screening, settling, and/or flotation (in which the extracted mixture was immersed in a solution that caused the undesired elements to sink to the bottom while the clay rose to the surface).
The mining industry as a whole has traditionally faced very high capital costs associated with its exposure to weather-related work interruptions, the cost of exploration activities and preparation of feasibility studies, the expense of acquiring and holding rights to mineral properties, the cost of purchasing and maintaining equipment, and the expense of developing and operating the mines and preparation plants. The mining operations of kaolin and ball clay producers were also governed by environmental regulations that required them to control dust emissions, reclaim strip-mined sites, and purify production waste materials.
Kaolin. The United States remained the world leader in kaolin production in the early 2000s. In 2002, 78 quarries in 10 states produced 8.01 million metric tons of kaolin, down from 9.45 million metric tons produced in 1998. About half of the kaolin produced was water washed. U.S. exports of kaolin in 2003, according to the U.S. Geological Survey, were estimated at about 3.40 million metric tons, and imports from foreign sources totaled approximately 275,000 metric tons. The primary supplier of kaolin imports was Brazil, which supplied 61 percent of the total despite the fact that it had just become a major supplier of kaolin in the late 1990s. In fact, imports from Brazil accounted for nearly all of the 117,000 metric ton increase in imports realized by the United States between
2002 and 2003. In 2003, total world production of kaolin was estimated at 45.1 million metric tons, with the Commonwealth of Independent States ranking as the leading producer worldwide after the United States.
Demand for kaolin, which is used primarily for paper coating and filler, was undermined by waning demand for paper, which had increased dramatically in price throughout the late 1990s and early 2000s; during this time period the paper industry had also suffered from the shift toward paperless transactions in the business world. At the same time, competition from calcium carbonate lessened demand for kaolin-based paper coating and filler products.
The leading U.S. producers of specialty clays in the early 2000s included Engelhard Corporation, which produced both kaolin and fuller's earth and posted 2003 sales of $3.7 billion and employed 6,650 workers, and J.M. Huber Corp., which secured revenues of $1.23 billion in 2002 and employed a workforce of 3,278. Other industry leaders included ECC International LTD; Thiele Kaolin Co.; and Dry Branch Kaolin Co.
Ball Clay. In 2002, the U.S. ball clay mining industry produced an estimated 1.12 million metric tons, up slightly from 1.11 million metric tons in 2001. The largest increase in demand and consumption was for sanitaryware. Positive sales for ball clay were attributed largely to the steady growth in construction, both commercial and residential, and home renovations. The construction segment provided consistent demand for sanitaryware, tile, and whiteware. However, competition from clay-based ceramic imports began to weaken this demand in the early 2000s. Ball clay exports in 2003 were 150,000 tons, according to the U.S. Geological Survey.
"Clays." Mineral Commodity Summaries. Washington, DC: United States Geological Survey, January 2004. Available from http://minerals.er.usgs.gov/minerals .
Virta, Robert L. "Clay and Shale." U.S. Geological Survey Minerals Yearbook. Washington, DC: U.S. Geological Survey, 2002. Available from http://minerals.er.usgs.gov/minerals .