Plate 32 



_ Another photomicrograph of no. 163. Taken with crossed nicols, magnification about 25 

 diameters. 



This method shows better the mineral habit of the rock with its coarse injection quartz and its 

 much finer feldspathic original content. 



Plate 33 



Photomicrograph of no. 395. Grenville gneiss. Taken with crossed nicols, magnification 

 about 45 diameters. 



Taken to show the mixed nature of a typical gneiss. This one is judged to be an injection or 

 impregnation gneiss in which the microcline can be clearly seen to cut or penetrate the other 

 feldspathic constituents. The microcline has a stringerlike distribution in this field and is perfectly 

 fresh, whereas the immediately adjacent orthoclase feldspar is much affected by sericitic alteration . 



The constituents are in part of Canada Hill type and in part are judged to be of Grenville source . 



