Explanation of Plate 2. 



Secondary Enlargement of clastic Tourmaline. 



Figure 1.— Secondary enlargement of elastic tourmaline pebble, showing prismatic 

 planes and slight development of terminal planes. Partially included 

 sericite prisms and occasional inclusions of quartz grains in new 

 growth. 



Figure 2. — Secondary enlargement of clastic tourmaline. The core is free from 

 interpositions ; the secondary mineral has abundant inclusions of 

 gneissic quartz aud feldspar. Many of the fissures of the core abut 

 abruptly against the new mineral, snowing two periods of straining. 

 The growing tourmaline is seen to have attacked a clastic area of 

 plagioclase, penetrating it irregularly and absorbing sericite previously 

 developed along cleavage lines. 



(106) 



