64 M1DDLEMISS: GEOLOGY OF HAZARA AND BLACK MOUNTAIN. 



I shall call these veins aplite veins (cf. Teall, " British Petrography, " 



p. 291). Although most of these veins can only be looked upon as 



being of an eruptive origin in the main, it is possible that segregation 



has had a certain share in the operation and brought about their 



diverse mineral composition. Of such an origin doubtless are the 



pegmatite veins of Panjigali m the Black Mountain, which occur 



among the ordinary gneissose-granite, and exhibit large schorl 



crystals and felspar crystals, together with a banded structure of 



finer quartz and felspar. 



The above mineralogical characteristics are, of course, common to 



a great many granites in a great many countries, 



Structure of the j-^ w j ien those characteristics are considered 

 gneissose-granite. 



in connection with peculiarities of structure, and 



when both are considered in connection with peculiarities of habit in 

 the rock as a whole, it is then that the close resemblance between 

 the gneissose-granite here, and in those parts mentioned by me in the 

 Lower Himalaya, becomes approximately demonstrated. 



The types of structure in the gneissose-granite may be divided 

 into the groups given below, which is a reproduction of the classi- 

 fication given originally by me. 1 



( (1) Tabular-foliated — absent or very rare in Hazara. 



(A) TOLIA ED < ^ L en ti cu i ar .t a i u i aY foliated— very common. 



C (1) Augen ^ 



(B) Semi-foliated j (2) PorphyfiHe augen j Common. 



(C) Non-foliated — Granitic — Common. 



Of these three groups, A, B, C, the last appears to be the original 

 condition in which the rock first solidified after intrusion among the 

 sedimentary rocks of the region ; whilst the modified forms, A and B, 

 have been, as a rule, derived from C by the mechanical action of 

 pressure metamorphism. General McMahon, I should mention, 

 regards similar foliated and semi-foliated gneissose granites of the 

 Himalaya as owing their structure to differential movements of the 



1 Rec. G. S. of I., Vol. XX, p. 139. 

 ( 64 ) 



