Photomicrograph of no. 74. Grenville schist. Taken with plain light, 

 magnification about 30 diameters. 



Taken particularly to show the minor structural features of a shear zone 

 schist of Grenville age. 



Composition chiefly epidote, quartz, feldspar, sericite and titanite. The 

 very streaked structure and augen structure are well developed, but this 

 particular specimen shows in addition, micro-faulting and tendency to 

 rhombohedral fracture. 



It is noticeable that the quartz is abundant only in lighter bands and is 

 either introduced or reorganized quartz, in either case essentially introduced 

 at this spot, whereas in some other occurrences of different date the shear- 

 zone material seems to be simply crushed and redistributed materials which 

 belong to the rock without any additions from without. It is possible that 

 this difference in content gives a clue to the age relation. In other words, 

 it is probable that this is a very ancient shear zone of Post-Grenville Pre- 

 cambrian age whose deformation is connected with the healing influences of 

 invading granite. In this case it is probably of Canada Hill age. 



