Ch. 25] CERAMIC PROCESSING PROBLEMS 473 



position, and the occurrence of the clay in the field are also essential. 

 It is frequently necessary to predict the occurrence of clays with 

 particular properties in a given deposit before it can be evaluated and 

 mined. In addition, the variable properties of a clay cannot be con- 

 trolled by beneficiation, and the variable properties cannot be com- 

 pensated for in processing unless the cause of the variation is known. 

 Evaluation of a clay deposit therefore should include a thorough 

 study of all aspects of the occurrence, origin, and composition to re- 

 veal the causes of any variations in properties of the clay. Many ex- 

 amples could be given to illustrate the importance of this, but one will 

 suffice. Certain beds of kaolin in the Georgia area contain small 

 amounts of montmorillonite in addition to the kaolinite. The presence 

 of montmorillonite does not change the appearance of the clay, and 

 in fact is not revealed unless a careful analytical study is made, yet 

 the presence of the montmorillonite changes the properties of the kaolin 

 so that it is not usable for certain purposes. Obviously any informa- 

 tion about the factors controlling the distribution of the montmoril- 

 lonite in the kaolin is of great importance to the kaolin producers. 



Search for Clay of a Particular Type 



The application of studies of the composition of clays to the search 

 for particular types of clay can best be shown by an illustration out- 

 side the field of ceramics. Some catalysts used in the making of gaso- 

 line are prepared from clays. Only a very few deposits of clay suitable 

 for this use have been found, and each clay has a particular composi- 

 tion and an origin which requires a certain geologic setting. A knowl- 

 edge of these factors obviously permits one to spot areas throughout 

 the world in which such clays are most likely to occur. 



Solution of Ceramic Processing Problems 



A plant ceramic engineer spends considerable time studying process- 

 ing problems which arise either because of variations in the processing 

 technique or because of variations in the raw materials being used. 

 The solution of problems of the latter type is expedited by a knowledge 

 of the composition of the raw material being used and its relation to 

 properties. Once the fundamental cause of the properties is known, the 

 solution to the problem is often obvious. For example, a clay plant in 

 a midwestern state operating on a series of glacial clays suddenly 

 found its percentage of rejected brick to increase greatly because of 

 lack of strength in the dried and fired brick. An examination showed 

 the presence of a lens of silt which had gone undetected. More 



