472 CLAYS AND CLAY INDUSTRY. 



MONMOUTH COUNTY. 



The clay deposits of Monmouth county are confined chiefly to 

 its northern and eastern portions, being found in the Raritan, Clay 

 Marl and Miocene formations. The second is represented by Clay 

 Marls I, II and IV, and the latter by the Asbury clay. 



Raritan and Clay Marls. 



Cliffwood and Keyport. — The Raritan clays have been dug at 

 numerous points in the vicinity of Cliffwood 1 (see map, PI. XII) T 

 while Clay Marl I is utilized in the line of brickyards located on 

 the left bank of Matawan creek below Matawan. Clay Marl II 

 has been utilized chiefly at the clay pits south of Keyport, and 

 Clay Marl IV, nowhere worked at present, contains some promis- 

 ing brick clay (p. 156). In addition to the localities where 

 the clay is dug, outcrops of all four formations are common along 

 the roads and numerous ravines which dissect this area. If the 

 physical characters of the clays from these different localities are 

 considered, there is no more difference between these three forma- 

 tions which are used than can be found in different pits of the same 

 formation, so that the clays from all three can be discussed to- 

 gether. 



The predominant type of unweathered clay in the region 

 around Cliffwood and Matawan is a black or bluish-black clay, 

 the clay layers being sometimes separated by laminae of sand. At 

 times these black layers are dense and fat, and even quite free 

 from grit, and in most of the pits the clays are found to contain 

 more or less lignite, pyrite and mica. They are commonly 

 weathered in their upper parts to different colors, such as yellow, 

 yellowish or reddish brown or chocolate. Concretions of limonite 

 may also be present in the weathered part. 



1 Several of the brickyards are just over the line in Middlesex county, but 

 are included here in order to discuss the district as a unit. 



