CLAYS OF MIDDLESEX COUNTY. 457 



Section at J. R. Cross-man's bank, Burt Creek. 



1. Yellow Cretaceous sand, 25 ft. 



2. Fat, yellow, sticky clay, 2^ " 



3. Blue clay, with some fine sand, 6 



4. Black, sandy clay, with lignite and pyrite, 8 



5. White clay, 2 



6. Blue fire clay No. 1. 



7. Red-mottled clay. 



A test was made of layer 6 (Lab. No. 409), which is regarded 

 as a good fire clay. It is lean, very fine-grained, and had a low 

 tensile strength, viz., 20 pounds per square inch. Its air shrinkage 

 was 6 per cent. Its behavior under fire was as follows : 



Burning tests of a No. 1 blue fire clay, J. R. Crossman, Burt Creek. 



Cone 5 8 



Fire shrinkage, 7% 11% 



Absorption, 19-35% n-59% 



Color, yellowish white yellowish 



This material is used as an ingredient of fire brick and stone- 

 ware mixtures. It becomes steel-hard at cone 5, but shows tiny 

 iron specks. The sample fused at cone 29, so that its refractori- 

 ness is not great enough to call it a No-. 1 fire clay according to the 

 classification adopted in this report. As indicated on page 451, 

 however, another sample of No. 1 blue fire clay from an adjoining 

 bank (Loc. 66) did not become viscous until cone 33, so that 

 there is evidently considerable variation in the fusibility of the 

 No. 1 fire clays in this vicinity. 



Chemical composition of a No. 1 blue fire clay, J. R. Crossman, Burt Creek. 



Raw. Burned. 



Silica ( Si0 2 ) , 40.64 47.27 



Alumina (AI2O3), 4I-I9 48-03 



Ferric oxide (Fe 2 3 ), 3.27 3.69 



Lime (CaO), 0.65 0.75 



Magnesia (MgO), trace trace 



Alkalies (Na 2 0, K2O), trace trace 



Water (H 2 0), 14.74 



100.49 99-74 



Total fluxes, 3.92 4.44 



