148 DETAILED REPORT ON ALABAMA CLAYS. 



grained and containing occasional reddish or pinkish 

 stains. There is no mica to be seen in it. It is hard 

 but very porous, and practically does not slake when 

 immersed in water for a long period. 



When mixed with 35 per cent, of water it gave a 

 gritty but lean mass, which had an air shrinkage of 4 

 per cent. In this case it had been ground to pass 

 through a 60-mesh sieve. When ground to pass 

 through a 100 mesh sieve it absorbed the same quanti- 

 ty of water but the plasticity was slightly increased, 

 while the air shrinkage remained about the same. 



At 2100 F. the clay burns white; at 2300 F. it is 

 white with a slight tinge of yellow, and at 2350^ F. it 

 is the same with the total shrinkage amounting to 

 only 4 per cent. Incipient fusion occurs at 2400 F. 

 and at cone 27 in the Deville furnace the clay vitri- 

 fied. 



The tensile strength is very low, not over 5 or 6 

 pounds per square inch. 



The chemical analysis yielded : 



Analysis of Fire Clay, near Valley Head, DeKalb Co. (No. 117). 



Silica 82.04 



Alumina 12.17 



Ferric oxide trace 



Lime trace 



Magnesia 327 



Alkalies 60 



Ignition 4.325 



99.462 



Total fluxes 927 



Specific gravity 2.38 



The rational composition is: 



Clay substance 31.10 



Quarts 64.80 



Feldspar 3.90 



99.90 



