FIRE CLAYS. 159 



(No. C. S.) 

 FLINT CLAY, 



CHOCTAW COUNTY. 



A hard, fine grained, siliceous clay, resembling flint 

 clay in appearance, but containing more silica than 

 such material usually contains. It presents a 

 smooth surface, with conchoidal fracture, and in wa- 

 ter practically does not slake at all. 



When ground to pass through a 30-niesh sieve it re- 

 quired 15 per cent, of water to make a workable paste 

 and was very lean and granular. The tensile 

 strength was, on the average, 5 pounds per square 

 inch. 



The shrinkage in drying was 2 per cent., and at 

 2300 F. 6 per cent. Incipient fusion occurs at 2300 

 F., vitrification at 2500 F. and viscosity at 2650 F. 



On anceount of its refractory qualities and IOTV 

 shrinkage, this flinty clay is admirably adapted for 

 admixture with plastic fire clays to serve as grog and 

 prevent undesirable shrinkage. The following two 

 analyses, No. 1, by W. B. Philips, and No. 2, by H. 

 Eies, give the composition of this material : 



Analysis of Fire Clay, Chootaw Co. (No. C. 8.) 



(1) (2) 



Silica (total) 86.30 85.70 



Alumina 5.12 6.15 



Ferric oxide 1.80 1.80 



Lime 46 tr. 



Water 6.60 7.00 



100.08 100.65 



Total fluxes 2.06 1.80 



Specify gravity 1.70 



*This is a Radiolarion clay, abundant in the Buhrstone division of the 

 Tertiary formation in many localities in Choctaw, Washington, Clarke, 

 Monroe and Conecuh counties. E. A. S. 



