•1 



i 



PLATE XXXIX. 



Fig. a. 



(Sp. No. 23321. Witli analyzer, x 35.) 



Photomicrograph of a section of hiotite-granite from the center of a dike 5 feet wide. On the 

 borders of the dilie the magma has crystallized as a normal mlca-diorite '.vithout qnartz and orthoclase. 

 (Described, p. 226.) 



FiCt. B. 



(Sp. No. 26023. With analyzer, x 35.) 



Mica-diorite showing tendency toward an ophitic texture. Plagioclase is the most automorphic 

 mineral. Biotite is next, but it is poorly developed. Orthoclase and quartz fill irregular areas 

 between the plagioclase. (Described, p. 231.) 



