588 T. L. WATSON LITHOLOGICAL CHARACTERS OF VA. GRANITES 



along the youngest or intersecting pegmatite. There is no evidence for 

 regarding this relation of the pegmatites as due to branching, but the 

 facts all support faulting as the cause. 



Those pegmatites which intersect the granite-gneiss in some cases 

 follow the schistosity, as in figure 1, and in other cases they cut across the 

 schistosity, as in figure 7. Plate 71, figures 1 and 2, are from photo- 



Fioure 6. — Faulted Pegmatite intersecting Blue Granite. 

 The Donald quarry, west of Richmond. 



graphs of pegmatites cutting the dark blue granite in the quarries at 

 Fredericksburg and Eichmond. 



Where observed, the pegmatites are sharply defined from the inclosing 

 rock; parallel banding to the walls does not occur; their composition is 

 essentially similar to that of the inclosing granite, and all of them are 

 entirely massive, without any evidence of pressure metamorphism shown 

 in them. This last feature, massive character, has an important bearing 

 on the question of the relative periods of formation of the pegmatites 

 and that of the granite-gneiss which they intersect. In case the gneiss 

 represents an original massive granite, which seems reasonably sure, it 



