CLAY-BEARING FORMATIONS. 365 



and for the manufacturer to make up mixtures of many different 

 properties. 



The fusibility of this same grade of clay is commonly high. 

 The best No. 1 fire clays do> not fuse below cone 35, but some 

 so-called ones may fuse at 30. The fusion point of the so- 

 called No. 2 fire clays commonly ranges from cone 27 to cone 33. 

 The stoneware clays show a refractoriness equal to' the good No. 

 2 fire clays, while many of the terra-cotta clays fuse at cone 27. 



To discuss the kinds of clay mined in the Raritan belt, and their 

 uses, would involve repeating much that is said on other pages, 

 and therefore reference is here made to- the description of the 

 clays of Middlesex, Mercer and Burlington counties (Chapter 

 XIX), and to the chapter on the Clay Mining Industry (p. 335). 



TRIASSIC SHALES. 



The Triassic shale is used for the manufacture of common 

 brick, and front brick at Kingsland, Bergen county, where very 

 fine-grained beds are quarried in the face of the bluff overlook- 

 ing the Hackensack meadows. The rock is moderately hard, 

 occurring in thick beds, and is quarried in large blocks which 

 are broken first by a jaw crusher and then pulverized in dry pans. 

 It has sufficient plasticity to be used in a stiff-mud machine, burns 

 to a good red color and makes a hard dense brick, but it becomes 

 viscous at cone 1. 



Samples of the shale from several other localities were tested 

 in the course of these investigations, but in all cases they were 

 too sandy and lacked plasticity, but beds equally as well adapted 

 to the manufacture of brick as those at Kingsland can undoubtedly 

 be found, although they may not be so favorably situated as 

 regards ease of working and transportation. 



HUDSON SHALES. 



This shale formation is for the most part too sandy for use 

 along these lines, but it is worked for clay products at one locality, 

 viz., Port Murray, where it is fine-grained and has been deeply 



