CLAYS OF CRETACEOUS FORMATION. 169 



is retained here, although only a part of the bed is a stoneware 

 clav. It is best shown at present in H. C. Perrine & Son's pits 

 southeast of South Amboy and the various banks at the base of 

 the bluff on the west side of Cheesequake creek. It has, how- 

 ever, been opened at a number o-f other places, although most of 

 these are no long'er worked. 



The upper portion of the bed is usually, but not always, a 

 black, more or less sandy clay, with some lig-nite and pyrite 

 ("sulphur"). It varies greatly in texture, being- sometimes al- 

 most a sand, and elsewhere rather a tough, black clay. Locally, 

 at least, its upper part was eroded by shifting tidal currents be- 

 fore the overlying sands were deposited. Moreover, this black 

 clay in places rests upon the sharply undulating", eroded surface 

 of the underlying stoneware clay proper, but this is not always 

 the case. Owing to the inequalities in its top and bottom- its 

 thickness varies greatly, ranging from nothing up to 18 feet. 



The stoneware clay proper, which underlies the black clay, is 

 generally a light-blue or white clay, carrying from one-third to 

 one-half its weight of fine quartz sand, 1 and very commonly con- 

 taining minute specks of iron sulphide or pyrite, as a result of 

 which it is often called "flyspeck" clay. In some pits a portion of 

 the bed is red mottled, and is regarded as of less value than the 

 light-blue or white clay. 



The thickness of the stoneware clay varies greatly, owing to its 

 partial erosion by tidal currents immediately after its formation, 

 and probably also to> differences in original deposition. In some 

 banks, as in H. C. Perrine & Son's (77), the old Ernst banks (80) , 

 and in the old clay mines of Morgan & Furman, thicknesses of 30 

 or even 35 feet have been found. The average thickness, how- 

 ever, is much less. 



In the bottom of the pits in the stoneware clay, there is found 

 either a black, lignitic sandy clay or a loose quartz sand. Our 

 knowledge of these beds, however, is limited to' the information 

 derived from borings, since they are nowhere exposed in a natural 

 section. A boring made many years ago by Otto Ernst, at his 

 pits near the mouth, of Cheesequake creek, showed 22 feet of sand 



1 Cook & Smock, loc. cit. p. 17. 



