358 CLAYS AND CLAY INDUSTRY 



weathered present beds of a dove-colored clay, which is generally 

 less granular than Clay Marl I, and breaks up into many blocks 

 when dry. (PL XVIII, Fig. i.) The weathered clay is also 

 of more open character, and sometimes less plastic than the 

 unweathered portion, which is dark gray, dense and plastic. The 

 overburden is either a sandy loam of post-Pleistocene age, beds 

 of Pensauken gravel, or sometimes a sand bed belonging to> the 

 overlying formation, Clay Marl III. This capping has often 

 protected the clay from discoloration and other changes due to 

 weathering, which, when overburden is not heavy, usually extends 

 to a depth of 6 to> 8 feet or even more. A secondary change 

 noticed in several of the deposits was the formation of masses of 

 limonite crusts. These do not form solid lumps, but are thin 

 streaks extending through the clay in many directions, and some- 

 times in such abundance as to form a perfect network. These 

 net-like masses may be very rare, or occur only in certain parts 

 of the bank, so that they can be avoided in digging the clay, 

 while at other times they permeate the entire deposit, practically 

 necessitating its abandonment. Only one instance of the exces- 

 sive development of these crusts was seen, viz., at locality 125, 

 west of Rancocas, where the sandstone crusts were all-prevading 

 in their extent and it is doubtful whether a deposit could be 

 worked under such conditions. 



In the field work a number of deposits located by Mr. G. N. 

 Knapp were tested by boring, and showed in most instances, at 

 least 6 to 7 feet of good clay, which is of course a very small 

 fraction of the total thickness of this formation. 



Samples were tested from fourteen different localities (see 

 table p. 360). The clay at two of these is being worked; the 

 other samples are, therefore, from deposits which are not being 

 used, and were either taken by boring into the deposit with an 

 auger or else by sampling the face of the bank. 



As compared with the clays of Clay Marl I, the samples all 

 show less mica and grit ; they are consequently more plastic, and 

 show higher air shrinkage. Some of them are even fat and 

 greasy. The samples from localities 231 (Lab. No. 607) and 

 129 (Lab. No. 608) represent weathered samples, and are plenti- 



