8 GRIESBACH : RAMKOLA AND TATAPANI COAL-FIELDS. 



granitic rocks north and south of the field, of from three to four 

 miles width on either side. Besides these, I came across several detached 

 masses of intrusive granite north of my area, as well as numerous peg- 

 matite veins in the older rocks, especially the old gneiss plateau of Chota 

 Nagpur. 



As near as possible, the boundary -hne of the granite with the meta- 



morphic rocks is parallel with the line of faults 

 Extent. / ^ 



which have lowered the Gondwana basin. An 



examination of the southern mass of granite between the villages of 

 Khijuria-t (east) and the limits of my map on the Mahan river (west) 

 shows that it probably includes both intrusive and metamorphic granite ; 

 but the hills are quite inaccessible, being covered by dense jungle and not 

 traversed by any roads or even jungle paths, so that a distinction could 

 not be made on the map. The section between the Mahadeva sandstone 

 on the north side and the Gobra hill on the south exposes a coarse-grained 

 granite, showing all the constituents of the granite in single hand-speci- 

 mens even, with isolated masses of garnet rock 

 Garnet rock. 



amongst it, the relation of which to the granite 



could not be ascertained. Near the Chalgali section the minerals com- 

 posing the granite get separated, and we meet there large masses of nearly 

 pure felspar with scarcely any quartz or mica in it. The best exposure 

 in the granitic ridge is seen along a rocky path leading from Lotki to 

 Bhagwanpur. Starting from the former place (Lotki), we soon leave 

 the mica schist (quartz schist) and enter the granitic ridge. There, veins 

 of granite traverse the schist for long distances, and prove beyond doubt 



the intrusive character of the rock. Towards the 

 Intrusive character. 



centre of the granitic ridge (about 3,000 feet high) 



we meet with a finer variety of granite, consisting of equal proportions 



of quartz, felspar, and white mica; but between 

 Lithology. 



that point and Lotki a coarse-grained porphyritic 



variety is seen, containing the same constituents, with tourmaline as 



accessory mineral, sometimes in large crystals. 



It is possible to find large blocks, consisting of nothing but milky 



( 136 ) 



