EXPLANATION OF PLATES. 

 PLATE III. 



Figure 16. 



Microphotograph of a small microcline crystal in the finer-grained portion 

 of the main pegmatite zone. The section is approximately parallel to the 

 base and shows twinning after the albitc law only. One set of lamellae are 

 in the position of extinction between crossed-nicols. Magnification about 

 150 diameters. 



Figure 17. 



Microphotograph of a basal section of microcline, cut from a freely de- 

 veloped crystal from the pocket. Shows twinning after the albite law only. 

 One set of lamellae are shown in the position of extinction between crossed- 

 nicols. Magnification about 350 diameters. 



