CLAYS 



125 



bonate can be substituted for many kaolin end 

 products; however, the comparatively low cost of 

 clays gives them a decided advantage over most 

 substitutes. Many construction products and raw 

 materials can be substituted very effectively for 

 brick, tile, and lightweight aggregate. A few of the 

 major ones are concrete, stone, glass, metal, plas- 

 tics, expanded slag, sintered fly ash, vinyl asbestos, 

 and cork. 



In 1969, the United States produced 58,694,000 

 short tons of clay, exported 1,574,000 short tons, 

 and imported 82,000 short tons (Wells, 1971, p. 

 287). The only clays imported in any large quantity 

 were kaolin and ball clay, but all six types of clay 

 were exported. Of the total clay production in 1969, 

 miscellaneous clay accounted for 72 percent; fire 

 clay, 12 percent; kaolin, 8 percent; bentonite, 5 per- 

 cent; fuller's earth, 2 percent; and ball clay, 1 per- 

 cent (fig. 14). 



In the United States, clay resources consisting of 

 material similar to that used currently are large, 

 but the clay deposits included in such resources may 

 not be ideally located for potential markets. Infor- 

 mation on clay resources in the rest of the world is 



1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 



Miscellaneous claVv^ ' 



1930 



1940 



Figure 14. — Production of miscellaneous clay, fire clay, kao- 

 lin, bentonite, fuller's earth, and ball clay in the United 

 States, 1920-70. 



not complete, but undoubtedly these resources are 

 enormous. 



KAOLIN 



The term "china clay" is somewhat synonymous 

 with kaolin, particularly for the raw material used 

 for ceramic products other than refractories. Kaolin 

 is white and easily dispersible and can be fired at 

 high temperatures without warping or changing 

 color. It is used primarily for coating and filling 

 paper, but other major uses are as fillers for prod- 

 ucts other than paper and refractories. Minor uses 

 include pottery, dinnerware, stoneware, and white 

 cement. Both kaolinite and halloysite are used in 

 the petroleum industry as petroleum-cracking cata- 

 lysts. Most kaolin is white, or nearly so, but shades 

 of red, yellow, and brown are common. Most of it 

 is plastic when wet, but some is hard and has flinty 

 characteristics of homogeneity and conchoidal frac- 

 ture. Although many kaolins are pure enough to be 

 used in their natural state for many purposes, most 

 kaolins are refined or are beneficiated by washing 

 or by several other processes. 



Five tons of kaolin was mined near Franklin, 

 N.C., and shipped to Josiah Wedgewood in England 

 in 1767-68. Since that time, the demand for kaolin 

 has increased so greatly that in 1970 production 

 reached almost 5 million short tons valued at slightly 

 more than $100 million. Georgia and South Carolina 

 are the major producers of kaolin, and small quanti- 

 ties are produced in Alabama, California, Florida, 

 Idaho, North Carolina, Pennsylvania, Texas, and 

 Utah. Kaolin production has increased at a nearly 

 constant rate during the past 50 years (fig. 14). 

 The depression in the 1930's and the recessions since 

 then have affected kaolin production less than any 

 of the other types of clay. The average value per ton 

 has increased from $5.75 in 1933 to $21.91 in 1968. 

 This undoubtedly indicates that increasing demands 

 for high-quality clay used for paper filler and paper 

 coater have caused production costs to rise steadily. 



Reserves of kaolin in the Cretaceous and Tertiary 

 rocks of the coastal plain of Georgia, Alabama, and 

 Mississippi are estimated to be more than 300 mil- 

 lion tons. Other deposits estimated to contain 1 

 million tons of kaolin are scattered throughout the 

 Appalachian region. The Nation's resources of kao- 

 lin, which contain a much higher percentage of im- 

 purities than the reserves, are estimated to be at 

 least 5 billion tons. This includes the potentially 

 recoverable kaolinite and halloysite found in sapro- 

 lite in North Carolina, California, Washington, and 

 Idaho, and the hydrothermal halloysite in Utah and 

 Nevada. 



