CHINA CLAYS. 127 



(N0.38S.) 



CHINA CLAY. 



J. J. MITCHELLS, CHALK BLUFF, MARION CO. 



Pure white, fine grained clay, brittle when dry, 

 and with conchoidal fracture. It slakes easily in 

 water, all of it passing through a 60 mesh sieve and 

 most of it through a 100 mesh one. 



The clay ground to pass through a 30 mesh sieve, 

 and mixed with 24 per cent, of water, gave a lean 

 mass whose air shrinkage was 4 per cent, and an addi- 

 tional shrinkage of 3 per cent, took place in burning, 

 giving a total of 7 per cent. 



Air dried briquettes of the clay gave the usual low 

 tensile strength of kaolin, the average being 15 pounds 

 per square inch, with a maximum of 17 pounds per 

 square inch. 



Incipient fusion occurs at 2300 F., vitrification 

 at 2600 P., annd viscosity at 2700 F. 



The clay burns to a clear white body. Its composi- 

 tion is as follows : ( No. 1 being by H. Kies and No. 2 

 by W. B. Phillips. No. 3 is the composition of pure 

 kaolin given for comparison.) 







Analyses of China Clay, Chalk Bluff, Marion Co. 



123 



Silica 47.25 47.20 46.30 



Alumina S6.50 37.76 39.80 



Water 13.35 14.24 13.90 



Ferric oxide 2.56 tr 



Lime tr tr 



Magnesia . . ." tr tr 



Moisture .50 tr 



100.16 99.20 100.00 



Total fluxes ( !) 2.56 



Specific gravity 2.44 



