116 DETAILED REPORT ON ALABAMA CLAYS. 



fusible ones to the very refractory bauxites, which are 

 unaffected by high temperatures. 



These investigations relate chiefly to those deposits 

 which have not yet been worked, with a view to aid the 

 development of Alabama's clay resources; and conse- 

 quently little is said with regard to the industry already 

 established. 



Where a number in parenthesis follows the name of 

 the locality, it refers to the number in the writer's note 

 book, unless succeeded by the letter S in which case the 

 number is that on the label furnished by Dr. Smith. 



The clays examined by me have been classified below 

 as follows: China Clays; Fire Clays; Potters' Clays; Brick 

 Clays; Miscellaneous Clays, and a few pages have been 

 added on the utilization of clays, in the manufacture of 

 Portland Cement. 



CHINA CLAYS. 



China clays might include those used in the manufac- 

 ture of porcelain and white earthenware, and of these, 

 two grades are recognized,!, e., kaolins, or china clay 

 proper, and ball clays. The former possess little plastici- 

 ty, a low percentage of fusible impurities, are generally 

 highly refractory and burn to a pure white body. Very 

 few kaolins can be put on the market in the condition in 

 which they are mined, and most of them have to be 

 washed in order to eliminate impurities which would tend 

 either to discolor the clay or to render the texture far too 

 coarse. The tensile strength of kaolins may vary from 5 

 to 15 Ibs. or even reach 25 Ibs., and the influence of this 

 low strength is overcome by the addition of plastic ball 

 clay. Iron is a very objectional impurity and should 

 not exceed 1 percent, indeed the less of it the better. 

 Alkalies, if present as silicates, are not wholly undesirable 

 for they serve as beneficial fluxes, but if contained in the 



