Plate 9 



Photomicrograph of no. 301. Grenville gneiss. Taken with plain light, magnification about 

 30 diameters. _ Silj 



Taken to show a specimen of quartz biotite siUimanite gneiss. The constituents are quartz and 

 feldspar (light smooth areas) biotite (black) sillimanite (light high relief rods) . 



Plate 10 



Photomicrograph of no. 501. An injection facies of Grenville from east side of quadrangle. 

 Probably largely Pochuck diorite in present make-up. Taken with crossed nicols, magnification 

 about 30 diameters. 



Showing: a Gneissic structure. 6 Abundant plagioclase (banded), c Abundant hornblende 

 (dark and rough with cleavage), d Abundant biotite (dark mottled with cleavage), e Much 

 less abundant quartz (clear) . / A little magnetite (dead black) . 



