432 CLAYS AND CLAY INDUSTRY. 



From these tests it would appear that this material was suitable 

 at least for the manufacture of common brick. 



Robbinsville. — Clay of the following composition is said to 

 occur near Robbinsville. 1 



Analysis of a clay near Robbinsville. 



Silica (Si0 2 ), 60.10 



Alumina (A1 2 3 ), 21.13 



Iron oxide (Fe 2 3 ), 6.07 



Water (H 2 0), 8.90 



Total, 96.20 



The analysis shows that it is probably red-burning, and not a 

 fire clay. 



Clay Loams. 



Trenton. — In the region around Trenton and as far north as 

 Pennington the clay loam which mantles the Trenton gravels and 

 extends back upon the hills to elevations of 200 feet (p. 121) 

 has been worked for a long* series of years for making .common 

 brick. The deposit is very shallow (PI. XV, Fig. 1), and con- 

 sequently large areas have been worked over. In fact the avail- 

 able supply near the yards has been nearly exhausted, and clay is 

 now brought in from points near Trenton Junction and Ewing. 

 These loamy clays around Trenton rarely run more than 5 or 6 

 feet thick and, moreover, may be pockety or basin-shaped in their 

 character. On account of the large number of stones which they 

 contain, they frequently have to be screened before use or put 

 through rolls to crush the pebbles. When burned they produce a 

 brick of excellent red color. Tests are given in the table facing 

 page 348. 



In the earlier years of the brick industry around Trenton, most 

 of the brick were made by the hand process, and those which were 

 sold for front brick were re-pressed in hand-power machines. 

 At the present time, however, the hand molding is still used for 

 the brick that are to be re-pressed, but the common brick are often 

 molded in steam-power, stiff-mud machines. 



1 Analysis by W. S. Myers, 1895. Unpublished. Exact locality unknown. 



