FIRE CLAYS. 151 



Analysis of Fire Clay, near Fort Payne, DeKalo Co. (No. 119). 



Silica 66.25 



Alumina 22.90 



Ferric oxide 1-80 



Lime trace 



Magnesia trace 



Alkalies 75 



Ignition 9.05 



100.55 



Total fluxes 2.35 



Specific gravity 2.28 



The rational analysis yielded : 



Clay substance 40.70 



Quartz 47.90 



Feldspar 11.20 



99.80 



(No. 112). 

 FIRE CLAY, 



FROM BIBBVILLE, BIBB COUNTY. 



This is one of the clays used by the fire brick works 

 at Bessemer, near Birmingham. For use it is mixed 

 with several other clays. 



The material itself, however, is a very sandy clay, 

 with much coarse grit and appreciable quantity of 

 mica. It is also abundantly stained with limonite in 

 places. When thrown into water it slakes fairlyfast 

 and falls to powder. It is quite a plastic clay, but in 

 working it up into a plastic mass it took only 22.6 per 

 cent, of water. 



The air shrinkage amounts to 6 per cent. At 

 about 2200 F. the clay burns creamy white, and 

 shows a total linear shrinkage of 9 per cent. While 

 at about 2300 F. incipient fusion is reached, with the 

 shrinkage the same, and the color buff. Vitrification 



