122 DETAILED REPORT ON ALABAMA CLAYS. 



CHINA CLAY. 



TWO MILES N. OFKYMULQA, TALLADEGA CO. (NO. 205.) 



A hard white clay, plainly stratified, due to the abun- 

 dance of many white mica scales arranged parallel with 

 the bedding. It is fine grained with a small amount of 

 fine grit. It slakes very slowly breaking into scaly frag- 

 ments. 



When ground to pass through a 100 mesh sieve it re- 

 quired 18 per cent, of water to mix it up, and give it a 

 mass which was only moderately plastic, owing to the 

 high amount of mica which it contains. 



The air shrinkage of the clay when thus mixed is 

 5 per cent. 



When burned to about 2200^ F, the color was pure 

 white, and the total shrinkage 8 J per cent., but incipi- 

 ent fusion had not been reached. 



At 2350° F, the color was white, and the total 

 shrinkage 11 per cent. 



In both cases the bricklets showed a tendency to 

 crack in burning. 



Incipient fusion occurred at cone 27 in the Deville 

 furnace, but at cone 30 vitrification was not complete. 



If used by itself it would probably not be safe to use 

 the clay in its raw condition above 2250° without devel- 

 oping a yellowish tinge, although* this migh not be no- 

 ticeable when ball clay and quartz and feldspar were 

 mixed. 



The mica interfers with the tensile strength just as 

 it did with the plasticity, so that the former did not ex- 

 ceed 15 lbs. to the square inch and varied between that 

 and 12 lbs. per square inch. 



