CLAYS OF MIDDLESEX COUNTY. 467 



Sayreville. — In the vicinity of Sayreville, the brick and fire- 

 proofing clays are dark-colored, gray to black, laminated, sandy 

 clays, with more or less lignite and often much mica. They also 

 contain scattered nodules of pyrite and limonite, and are fully as 

 extensive as the similar clays belonging to> the same beds on the 

 north side of the Raritan river. Owing to< the size of the deposits, 

 and little need of separating the different layers, the material is 

 often mined with a steam shovel. It is then loaded directly on 

 to cars and hauled to the works either with a small engine or 

 horses. 



These clays in their physical character resemble those found 

 near Keasbey. They are red-burning, nonrefractory clays, which 

 become steel-hard at a low cone, but have to be fired somewhat 

 slowly in the early stages of burning. The two following series 

 of tests will indicate their character : 



1. Common-brick clay from pits of the Sayre & Fisher Com- 

 pany, at Sayreville (Loc. 71, Lab. No. 393). This clay, which is 

 quite micaceous and sandy, splits up rapidly along the planes of 

 stratification when thrown into water and then slakes to powder. 

 It took 30.5 per cent, of water to work it to a plastic mass, whose 

 tensile strength ranged from 70 to 75 pounds per square inch. 

 The air shrinkage was 4 per cent. Its behavior in burning was 

 as follows : 



Burning tests of a common-brick clay, Sayre & Fisher Co., Sayreville. 



Cone 01 1 5 8 



Fire shrinkage, 6% 6.6% 7% 8% 



Absorption, 10.17% 9-30% .... 



Color, red red brown deep red brown red gray 



It burned steel-hard at cone 01 and fused at cone 12. Its com- 

 position is : 



Chemical analysis of a common-brick clay, Sayre & Fisher Co., Sayreville. 



Silica (Si0 2 ), 60.18 



Alumina ( AI2O3) , 23.23 



Ferric oxide (Fe-0 3 ) , 3.27 



Lime (CaO), 1.00 



Magnesia (MgO), '. 0.67 



