176 DETAILED REPORT ON ALABAMA CLAYS. 



(No. 70S.) 

 POTTERY CLAY. 



W. DOTY, PAYETTE CO. 



A fine grained, rather gritty, reddish clay. In water 

 it'slakes quickly to small irregular grains. The addition 

 of 25 per cent of water gave a plastic mass, which shrunk 

 6.2 per cent, in drying and an additional 5.8 per cent, in 

 burning, giving a total shrinkage of 1 2 per cent. 



Briquettes of the air dried clay had an average tensile 

 strength of 95 pounds per square inch, and a maximum 

 of 151 pounds. 



Incipient fusion occurred at 2000 F., and viscosity at 

 2400 F. The clay burns to a yellowish color at 2000, 

 but to a red at 2200. The body of the burned clay is 

 smooth and dense. 



The clay analyzed as follows: 



Analysis of Pottery Clay, W. Doty, Faette Co. (No. 70 S.) 



Silica (total) 67.10 



Alumina 19.37 



Water 6.08 



Ferric oxide 2.88 



Lime tr. 



Magnesia 725 



Alkalies 672 



Moisture 1.71 



98.537 



Free silica (sand) 43.93 



Total fluxes 4.27 



Specified gravity 2.416 



In cornpositon this clay resembles some-what a clay 

 used for pottery and sewer pipe, and obtained at Gilker- 

 son Ford, Henry Co., Mo.* 



*Mo. Geol. Survey XI, p. 528. 



