BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 17, PP. 523-540, PLS. 69-72 DECEMBER 31, 1906 



LITHOLOGICAL CHARACTEKS OF THE VIRGINIA 

 GRANITES* 



BY THOMAS LEONARD WATSON" 



(Presented by title before the Society December 29, 1905) 



CONTENTS. 



Page 



Introduction 523 



The Virginia Piedmont region 524 



Geology 524 



Distribution of the granites , 524 



Mineral composition of the granitesi 525 



Kinds of granite , 525 



Even granular granites , 526 



Introductory statement 526 



Petrography of the granites 526 



The Richmond-Petersburg light gray granite 526 



The Richmond-Fredericksburg dark blue granite 528 



The Fredericksburg light gray granite 529 



The Falls Church types 529 



The Annandale type 530 



Unakite 530 



Porphyritic granite 531 



Granite-gneisses 532 



The Richmond-Fredericksburg gneiss 533 



Structural relations of the granites in the Richmond-Fredericksburg areas 533 



Types 533 



Contacts 534 



Apophyses 535 



Inclusions 535 



The aplites and the pegmatites 536 



Joint systems 539 



General character 539 



Horizontal joints 539 



Introduction 



The general excellence of the Virginia granites as a building and mon- 

 umental stone is well established in the commercial world. Notwith- 



*The writer is indebted to Dr H. Ries for taking the photographs from which the half-tone 

 of this paper were made. 



XLVIII— Bull. Geol. Soc. Am., Vol. 17, 1905 (523) 



