POTTERY OR STONE WARE CLAYS. 173 



(No. 11 S.) 

 POTTERY CLAY. 



CBIBBS PLACE, BEDFORD, LAMAR CO. 



A d^rk- colored, tough blue clay, containing much or- 

 ganic matter. It is very dense, and slakes very slowly. 

 No pyrite and few mica scales were noticeable. 



It requires 45 per cent, of water to make a workable 

 mass, which was extrremely plastic and fat. This clay 

 shrunk 12.5 per cent, in drying and an additional 6.5 per 

 ceat. in burning giving a total shrinkage of 19 per cent., 

 which is a large amoumt. The tensile strength of this 

 air dried briquette should be great, but on account of 

 the excessive plasticity it was found hard to mould bri- 

 quettes which were free from flaws, so that most of them 

 broke at about 100 pounds per square inch. Incipient 

 fusion occurs at 1900 F. Vitrification at '^100 F. and 

 viscosity at 2300 F. 'The clay burns to a deep red, 

 dense body. 



The following is the composition of it. 



Analysis of Pottery Clay, Cribbs' Place, Lamar Co. (No. 11, 8.) 



Total silica 60.9 



Alumina 18.98 



Water and organic matter 12.46 



Ferric oxide 7.68 



Lime trace 



Magnesia trace 



Alkalies trace 



Moisture 90 



100.92 



Free silica (sand) 37.92 



Total fluxes 7.68 



Specific gravity 2.313 



The chief use of ihis clay won Id probably be as a bond 

 for leaner clays, in the manufacture of courser grades of 

 pottery, or perhaps sewer-pipe. 



