CRYSTALLIZATION OF DIKE AND STOCK ROCKS. 



113 



as in the case of the group of dike rocks. In general, quartz and. biotite 

 are more abundant in the more acid varieties of the coarse-grained rocks, 

 but they both appear in the basic varieties when they are coarsely crystal- 

 line. The relations of hornblende and pyroxene to the chemical composi- 

 tion of rocks are not elucidated in any way by the study of this group of 

 rocks. It is evident, however, that in the intrusive rocks of this region 

 hornblende is developed to a greater extent in the basic rocks, in propor- 

 tion as they are coarser grained, and that pyroxene is more abundant in the 

 finer-grained forms than in the coarser. 



The mineral composition of the quartz-mica-diorite-porphyry, Group 

 III, is very uniform, and needs no tabulation. It contains very much 

 quartz, abundant biotite, and almost no hornblende ; the greater part of the 

 rock is more siliceous than the main body of the diorite, and reaches 69.24 

 per cent of silica, but a facies of it which is richer in hornblende than the 

 body of the rock has only 65.97 per cent of silica. 



Table VIII. — Grades of crystallization of the dike and stock rocTcs of Electric Peal\ 



Grade. 



I. 



II (a). 



11(6)'. 



II (e). 



III. 



d] to rf ]0 . 



>,. 



s 2 . 



«3- 



s 4 and rf n . 



6 











259 

 260, 261 

 262, 263 



264, 265 



7 



240 



238 



r 239 



I 241, 242 



243, 246 



1 244, 245 



1 254, 256 



i 239, 249 



l 250, 257 



251 



(■ 247, 248 



l 252, 253 









8 









9 



10 



1 







f 







11 

























13 



14 



15 











266 

 267 



268 



269 

 270 





















16 



17 



235, 254 









301 

 302, 303 



304 



305, 306 



307 







18 









IS 



20 



< 232 



I 236, 237 



233 



! 



314, 315 





324, 325 

 326, 327 



21 







1 





