i8o CLAYS AND CLAY INDUSTRY. 



Section near Crossman's dock, Burt Creek. 



a. Quartz sand, 20 ft. 



b. Chocolate sandy clay, 6 " 



c. Quartz sand with lenses of "feldspar," 14 " 



d. Fine mica sand and "kaolin," 6 " 



Total, 46 " 



f. Black laminated clays of the Woodbridge member. 



No section is known in the State nor any boring embracing the 

 whole of this subdivision, but it is believed that the total thick- 

 ness does not greatly exceed the maximum given above. Prob- 

 ably a thickness from 40 to 45 feet would be not far from the 

 average. 



As was pointed out in the earlier clay report, 1 the terms "feld- 

 spar" and "kaolin," as used in the Woodbridge district are mis- 

 applied. The "feldspar" is a coarse, arkose sand or gravel, i. e. T 

 a mixture of quartz, and more or less decomposed feldspar and 

 pellets of white clay, together with extremely minute amounts of 

 other minerals. Hornblende or pyroxene and undecomposed 

 granitic pebbles occur very sparingly. In the most typical beds the 

 quartz amounts to about 60 per cent, by weight and 50 per cent, 

 by volume. 2 



The feldspar pebbles occur up to- an inch and a half in diameter, 

 but the bulk of the material is much finer. Nearly all the feldspar 

 has. been decomposed to a white clay, a nearly pure kaolinite, but 

 occasionally pebbles of unaltered feldspar are found, which still 

 show planes of cleavage on their fractured surfaces. Many of the 

 kao'linized masses, however, are not pebble shaped, but are irreg- 

 ular in outline and are squeezed around the quartz pebbles. The 

 quartz pebbles are generally rounded or at least subangular, and 

 lack the sharp edges and corners of grains which have not been 

 waterworn. 



The "feldspar" beds occur as local lenses, which thicken and 

 thin, pitch steeply or extend horizontally, and vary greatly in 

 composition within narrow limits. The accompanying sands are 



1 Report on Clays of New Jersey, 1878, p. 61. 

 2 Loc. cit. p. 63. 



