Plate 15 



Photomicrograph of no. 430-&. Reservoir granite. Taken with plain light, magnification about 

 30 diameters. 



Same as last slide with a different field to show other characteristic make-up. The minerals 

 are: a Large areas of soda-feldspar, b Many small grains of quartz, c Many large and small 

 flakes of biotite. d A very large grain of allanite. e A garnet area of irregular outline, f Very 

 small amount of zoisite and other accessory minerals. 



Plate 16 



Photomicrograph of no. 16-6. Reservoir granite. Taken with crossed nicols, magnification 

 about 30 diameters. 



Slide shows a field with an unusually strong schistose and granular habit. The structural quality 

 in this case is emphasized by the streaks of finer material, the granulation of some of the more 

 brittle material and the orientation of the mica flakes developed along lines of weakness even 

 cutting some of the other grains. The principal constituents are: a Soda-feldspars and orthoclase. 

 b Quartz, mostly in aggregate form, c Biotite, mostly oriented, d Epidote, zoisite and small 

 amount of other minor constituents. 



The structure is the most characteristic thing about this field. 



