176 



PROCEEDINGS OF THE ACADEMY OF 



[Part I 



(fig. 1). Small irregular dikes occur also in Brinton's serpentine 

 quarries, three miles south of West Chester (fig. 2). Extensive 

 quarries lie west and northwest of Sylmar in Chester County, and 

 southeast of Rock Springs, and northeast of Pilot, Cecil County. 

 In two cases, east of Bald Friar, and a mile northeast of Pilot, Ce- 

 cil County, quarries have produced commercially both albite and 

 talc. But two quarries are at present worked: Wiant's quarry 

 three-quarters of a mile northeast of Pilot, and Garrison's quarry, 

 three-quarters of a mile east of Rock Springs, Cecil County. The 

 others are abandoned and filled with water, but their size gives 

 evidence of the great quantity of albite which they formerly pro- 

 duced. 



The albitite dikes range in size from a few inches in width, such 

 as at Brinton's quarry, south of West Chester (fig. 2), to great 

 masses four or five hundred feet in length, and more than a hundred 

 feet in width, such as were quarried at the Rock Springs quarry, 

 and at the Sparvetta, Keystone, and Brandywine quarries, one 

 and a half miles west of Sylmar, and at Campbell's quarry, two 

 miles northwest of Sylmar. 



Fig. 3 



Fig. 4 



One hundred feet 



Fig. 3. — Horizontal section of an albitite dike quarried one and a quarter miles 

 northwest of Sylmar, Chester County, Pennsylvania. 



Fig. 4. — Horizontal section of an albitite dike quarried two miles northwest of 

 Sylmar. 



