0^ KAMCURIl COAL TIELD. 



These bosses occ-ur most abundantly south of the Eamgurh field ; 



as we approach the south boundary of that field. 



Position of bosses. ^^ g^^ ^^^ porphyrytic gneiss is overlaid by the 



oranitic and syenitic varieties ; these also occasionally form bosses, in 

 which, however, the s/iell structure is not so well developed. 



Above these last are found quartzites, felspathic gneiss, and mica- 

 schists, alternating with homblendic schists. The 



'^^ ^°^ ^' quartzites are less frequently met with than the 



other varieties. They seldom consist of pure silica; more frequently 

 containing either a small proportion of felspar or a few scattered crystals 

 of mica. 



The mica-schists, too, occur but seldom in the sections. Near the 

 Mica-schists. village of Bulsugra, west of the Bokaro field, they 



seemed to be more strongly developed than elsewhere. 



The homblendic schists display their ordinary €haracters, i. e., some 



are distinctly foliated, while others are compact and 



Horn en c sc is s. ^f^gn undistinguishable from greenstone ; while 



still another variety, owing to the absence of foliation and the distinct 



crystallisation of the component minerals, might easily be mistaken for 



a diorite. 



Towards the south boundary of the Bokaro field occur a number of 

 north and south ridges of sandstone-like gneiss and 

 an s one- 1 e gn i . j^Qrublendic schists. The former, when slightly 

 disintegrated, is not easily distinguishable from an ordinary coal-measure 

 sandstone. The latter correspond to the varieties of homblendic schists 

 already mentioned ; the chief difference being that the cannon-ball struc- 

 ture is better developed, or perhaps it may be only more favorably 



exposed. 

 (134) 



