50 F00TE: GEOLOGY OF THfc) BELLARY DISTRICT. 



A remarkable gneissoid rock of beautiful green colour, due to 



cupreous staining, occurs in the corner of the 

 dreen gneiss. > ° 



hills three miles east of Hirahal (Hirrahall of 

 sheet 59). Owing to the great extent and thickness of the super- 

 ficial deposits, talus and soil there occurring, the relationship of this 

 gneissoid rock is open to doubt. In position stratigraphically it ap- 

 pears to belong to the Dharwar system, but petrologically it would 

 seem to belong to the gneisses. Fragments of bright green quartz, 

 derived from this or some other similar bed, are not unfrequently met 

 with on the surface of the great talus shingle bed which lies along the 

 southern foot of the Minchary hills, as the eastern end of the Copper 

 Mountain synclinal ridge is frequently called. This green quartz is 

 often of such rich and pleasing colour that it might well be used for 

 decorative work as mosaic, &c. It was probably from this and from 

 a green gneiss bed near Halkundi, mentioned further on, that the old 

 celt-makers of the Bellary and other neighbouring neolithic settle- 

 ments derived the green micaceous stone they so much affected in the 

 preparation of u mealing stones," and which they took the trouble 

 to fetch from very considerable distances. 



The rocky wilderness which lies to the south-west of Hirahal is 



Wilderness south- formed of the quartzo-felspathic granite of 



west of Hirahal. the group «£» of the c i ass ifi ca tion given on 



p. 25. It is a rough surfaced (trachytoid), irregularly jointed, small 

 block-forming variety which recurs again largely to the north-west, 

 occupying, indeed, nearly the whole remaining part of the sub- 

 division and making it very rugged and stony. 



The felspathic granitoid is largely permeated by small veins of 

 pegmatite, and large portions of the rock itself have acquired a very 

 strongly pegmatoid appearance and texture, but without any visible 



cause for such change. This feature is frequently to be seen wherever 



this form of granitoid prevails. 



Near the west end of the great Avinmadugu tank is a group of 



low hills consisting of very fine grained massive felspathic granite 



gneiss containing black mica. 



( 50 ) 



