SS MIDDLEMISS: GEOLOGY OF HAZARA AND BLACK MOUNTAIN. 



between the more metamorphosed and the less metamorphosed : the 

 two extremes of type grade into one another by many a passage 

 form ; and (2) the agent by which the metamorphism has been 

 produced (as will be afterwards shewn), namely, the intrusive 

 gneissose-granite, continues of the same general composition, struc- 

 ture, and habit through the whole breadth of the metamorphosed 

 strata, being found alike among the slightly altered arenaceous 

 schists of Mansehruh and the well-foliated examples now to be de- 

 scribed. 



Mica-schist from the locality marginally-noted No. gf F appears 

 in the hand-specimen as a beautiful thoroughly- 



Junction of Shal N. , , . , 



with Indus river, Black well foliated schist, the pale mica being very 

 prominent on the foliation planes. Black mica 

 can also be discerned in small quantity. 



Under the microscope the structure is seen to be that of a typical 

 mica-schist. The layers of granular, quartz, pale and brown mica, 

 lie in almost perfect parallelism. Besides the above minerals, there 

 are very minute irregular isotropic bodies with a high refractive index 

 which are most probably garnets. There is no mylonitic structure 

 visible, and whatever crushing the rock sustained originally has been 

 entirely masked by the thorough re-crystallization of the mass. No 

 trace of an ultimate clastic origin can be detected. 



A slightly garnitiferous mica-schist from 50 yards east of the last 



locality, No. -§-§ f , is of a darker colour, due to the 



, 5 ° 7 ar al - s t eas ° larger proportion of black mica contained in it. 



Like it, however, it is a thoroughly crystalline 



schist devoid of crumpling or corrugation and the folia perfectly 



parallel. A small amount of felspar is noticeable. The microscope 



confirms the above. White mica is seen to be completely absent. The 



garnets are larger than in g-f 3- and shew ragged outlines and evidence 



of crushing or else of imperfect development. The plates of brown 



mica wave round the garnets in places. There are a very few 



examples of felspars also with ragged outline, some shewing binary 



twins. All the flespars are crowded with minute needle-like inclu- 



( 58 ) 



