Plate 6 



Photomicrograph of no. 143. 



Taken with plain light. 



magnification about 30 diameters. QuartzHbiotite-garnet-gneiss. 



Taken to show the habit of the rock and especially its content of garnet. 



The constituents are quartz, crthoclase and acid plagioclase (all clear and 

 smooth in this photomicrograph), biotite (dark gray and black plates), and 

 garnet (gray rough grains). 



