Plate 25 



Photomicrograph of no. 373-a. Magnetite schi^ (Grenville). Taken with plain light, magnified 

 about 30 diameters. 



Taken in this light to show mineral association and structure. 



a Magnetite (dead black), b Pj-roxene (dark and rough), c Quartz and feldspar (clear). 

 d Apatite (white stronger relief) . 



Plate 26 



Photomicrograph of no. 373-^-x. Majnetits-schist. Taken with crossed nicols, magnification 

 about 30 diameters. 



This field shows the structure and mineral make-up of this rock. 



a Quartz (clear and with strain shadows), b Striated feldspars (a few grains), c Magnetite 

 (dead black grains) . d Pyroxene (rough grains) . 



