MARYLAND GEOLOGICAL SURVEY 217 



erty of Frank Weeks, near Pleasant Hill. The material contained 

 an abundance of micaceous scales. At cone 27 it burns white, with 

 the merest trace of yellow, and is but incipiently fused. 



Kaolin is also known at Jackson's Baltimore and Ohio Railroad 

 crossing north of Northeast. 



Flint and Feldspar. 



Quartz of sufficient purity and abundance to stimulate attempts at 

 quarrying it for " flint " has been found in many places throughout 

 the northern part of Cecil county, especially in the vicinity of the 

 serpentine " barrens." It occurs in veins or dikes trending in a north- 

 easterly direction from the Susquehanna, more or less nearly parallel 

 to the boundaries of the different rocks. The presence of " flint de- 

 posits " is indicated by the numerous boulders of white vitreous 

 quartz which often appear honeycombed. The veins in which the 

 quartz occurs cannot be traced for any considerable distance in Cecil 

 county, and there are no bodies as large as those about Castleton 

 across the river in Harford county. There are, however, several 

 places where small openings have been made for quarrying the 

 " flint," which is hauled to the mill at Conowingo. At the present 

 time most of the flint ground at Conowingo comes from Harford 

 county. It is customary to roast the blocks of quartz in the kiln 

 shown in Plate XIX, Fig. 2, and then cool it suddenly by pouring 

 water on the highly heated rock. This cooling causes a rapid con- 

 traction, which in turn causes the rock to be filled with cracks which 

 render the grinding much easier and more economical. The ground 

 flour of flint is shipped in bags to the potteries located at Trenton, 

 New Jersey, and elsewhere. 



Feldspar has been quarried from time to time in Cecil county. 

 This mineral occurs in pegmatitic veins which are found in different 

 parts of the highlands of the county underlain by crystalline rocks. 

 These veins or dikes are best exposed along the Susquehanna river 

 in the northwestern part of the county, as already described by Miss 



