74 MIUDLEMISS: GEOLOGY OF HAZARA AND BLACK MOUNTAIN. 



than the last. The rock is more quartzose than an ordinary gneiss 

 or granite, the quartz being present in the usual polysynthetic aggre- 

 gates, but so abundant, together with a large amount of brown mica, 

 that one is tempted to regard the rock as a mica-schist among which 

 a few felspars have migrated from the neighbouring gneissose-granite. 

 The latter shew carlsbad twins, but their outlines are very ragged and 

 broken. 



No. -gfe-, junction of Shal N. with Indus. A vein in foliated 

 dark mica-schist. Under the microscope it shews patches of various 

 degrees of fineness, indicating either a euritic or microgranulitic 

 ground-mass, or as seems more probable a final stage in the pressure 

 metamorphism of a normal granite in whieh the felspars, full of inclu- 

 sions, have become almost entirely destroyed, there being nothing 

 left of them but extremely ragged fragments. Quartz is present in 

 the usual polysynthetic grains. Garnets are very prominent in idio- 

 morphic grains at the edge of the vein in the micaceous part of the 

 enclosing schist. 



No. F $3, i mile north of Mansehruh. A foliated variety from near 

 a trap dyke. It exhibits beautiful microcline-like and finely twinned 

 effects in the felspars, and sometimes also apparently microperthitic 

 intergrowths : carlsbad twins prominent, and in situ breaking-up and 

 powdering of the margins of the quartz and felspar, with production 

 of mylonitic structure. Brown mica, white mica, and tourmaline are 

 present. 



No. ¥ f-g-, Shal N., Black Mountain. A hypersthene granitite 

 (foliated). This rock, which 1 have not found elsewhere in the area 

 described by me, contains quartz, felspar (chiefly triclinic), mica, and 

 hypersthene. The presence of hypersthene in so acid a rock with 

 free quartz recalls the charnockite recently described by Mr. Holland 

 from the Nilgiri and Shevaroy Hills, Madras. The hypersthene is 

 apparently being converted into brown mica. The rock has been 

 well foliated by pressure. It is possible it may be genetically related 

 to the ultra-basic rock No. ^| T to be presently described. 

 ( 74 ) 



