UNITED STATES MINERAL RESOURCES 



CLAYS 



By John W. Hosterman 



CONTENTS 



Page 



Abstract of conclusions 123 



Introduction 123 



Kaolin 125 



Ball clay 126 



Fire clay 126 



Bentonite and fuller's earth 127 



Miscellaneous clay 128 



Summary of resources 129 



Environmental considerations 129 



Problems for research 129 



Selected bibliography 130 



FIGURE 



14. 



Production of miscellaneous clay, fire clay, kao- 

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

 the United States, 1920-70 



TABLE 



25. Summary of clay resources of the United States 



Page 



129 



ABSTRACT OF CONCLUSIONS 



Clays are naturally occurring rocks composed of fine par- 

 ticles that are principally hydrous aluminum (or magnesium) 

 silicates. They occur as deposits that are divided for com- 

 mercial purposes into kaolin, ball clay, fire clay, bentonite, 

 fuller's earth, and miscellaneous clay. Resources of clay de- 

 posits similar to those used currently are extremely large, 

 except for those of high-grade ball clay and high-grade 

 colloidal bentonite. The geologic profession could be of bet- 

 ter service to the city, county, and State planners, the clay 

 producers, and the consumers of a wide variety of clay 

 products if geologists doing areal geologic mapping, par- 

 ticularly near metropolitan areas, were more aware of the 



economic potential of clay occurrences in the area being 

 mapped. Attaining such awareness may require the making 

 available the necessary equipment and procedures to evaluate 

 the economic potential of the clay occurrence. 



INTRODUCTION 



Clay was first used in the United States by the 

 Indians for making pottery. It has been used ex- 

 tensively as the building material for adobe, a sun- 

 dried mixture of clayey loam, straw, and water since 

 the time of the early Spanish settlers in the south- 

 western part of the country. Clay was first used in 

 this country in 1585 to make building brick at the 

 Raleigh settlement on Roanoke Island, N.C. Dr. 

 Danial Coxe, an early governor of West New Jersey, 

 was probably the first to make pottery in the Colo- 

 nies, when he built a plant at Burlington, N.J., 

 about 1685. White clay is reported to have been first 

 mined by the Indians in western North Carolina; 

 and was exported to England in the early part of 

 the 17th century. 



Clays are naturally occurring rocks, both uncon- 

 solidated and consolidated, composed of very fine 

 particles of clay minerals that principally are lay- 

 ered hydrous aluminum (or magnesium) silicates 

 but may contain varying amounts of iron, potassium, 

 sodium, and other ions. All deposits of clay contain 

 other minerals, and these impurities are rare in 

 some deposits but abundant in others. The most 

 common other minerals are quartz, mica, feldspar, 

 iron oxides, and carbonates. Titanium-bearing min- 

 erals and gypsum are abundant in some deposits; 

 organic matter, such as carbon or kerogen, is abun- 

 dant in others. 



Most deposits of clay have as their major compo- 

 nent, one of the following clay minerals : Kaolinite, 

 halloysite, montmorillonite, palygorskite, and illite. 

 Some clay deposits may contain one or more of these 

 clay minerals as a minor constituent. The U.S. 

 Bureau of Mines has classified clay deposits into 



U.S. GEOL. SURVEY PROF. PAPER 820 



123 



