ARGILLACEOUS ROCKS: PBLITES 



117 



disintegration more through physical than chemical agencies, as 

 will be noted later. 



Chemical Composition op Glatjconitic Marls 



Constituents 



I 



II 



III 



IT 



V 



VI 



vn 





% 



% 



fo 



fo 



fo 



% 



% 



Phosplioric acid . . . 



. . 



1.15 



0.58 



1.51 



0.19 



0.50 



6.87 



3.73 



Sulphuric acid . . 









1.28 



• . . • 



2.40 



0.41 



0.34 



3.12 



2.44 



Silica and sand . . 









34.50 



45.50 



55.69 



51.15 



47.50 



44.68 



49,68 



Potash 









1.54 



3.79 



5.27 



7.08 



5.29 



3.97 



4.98 



Lime . , . . , 









2.52 



1.51 



0.65 



0.49 



0.56 



4.97 



4.14 



Magnesia . . . , 









2.15 



2.20 



0.79 



2.02 



2.70 



2.97 



0.47 



Alumina . . . 





. 





6.00 



5,80 



6.61 



8.23 



8.60 



6.04 



9 



* 



Oxide of iron . , 





. 





31.50 



24.50 



21.63 



23.13 



20.52 



18.97 



28.71 



Water .... 





• 





18.80 



15.40 



8.85 



6.67 



13.57 



8.63 



5.54 











99.43 



99.18 



102.40 



99.37 



99.58 



99.32 



99.69 



I. Clay marly from near Mattawan. II. Clay marl, from Mateliaponix 

 Creek, three miles south of Spottswood. III. Lower marl, from Navesink 

 Highlands. IV. Middle marl, from near Eatontown. Y. Middle marl, from 

 southeast of Freehold. VI. Upper marl, from Poplar. VII. Upper marl^ 

 from Shark River. 



(2) The Argillaceous Group: Pelites. — The rocks of this 

 group are composed of more or less hydrated aluminous sili- 

 cates admixed in almost indefinite proportions with siliceous 

 sand, various silicate minerals in a more or less fragmental and 

 decomposed condition, and calcareous and carbonaceous matter. 

 In their least consolidated form they are best represented by 

 the common plastic clays used for brick and pottery manufac- 

 ture. Such, although alike in their general physical or even 

 ultimate chemical nature, have widely diverse origins. In fact, 

 the term day^ like sill, indicates physical condition rather than 

 chemical or mineralogical composition, and it may perhaps be 

 defined as an indefinite admixture consisting largely of more or 

 less hydrated aluminous silicates and free silica, with lesser 

 amounts of iron oxides, carbonates of lime, and various silicate 

 minerals which in a more or less decomposed and fragmental 

 condition have survived the destructive agencies to which they 

 have been subjected. About the only feature characteristic of 

 all clays, is that of plasticity, when wet, and this is dependent, 



