HATCH: THE KOLAR GOLD-FIELD. 



CHAPTER I. 



GENERAL GEOLOGICAL DESCRIPTION OF THE FIELD. 



The belt of schists in which the quartz veins of the Kolar gold-field 

 occur is a part of the great group of Transition Rocks. This and 

 other similar schistose belts were first separated by Bruce Foote 1 

 from the old gneisses with which they had till then been classed, and 

 given the name 4< Dharwars " or " Dharwar System " on account of 

 their occurrence in typical development in the Collectorate of Dhar- 

 war, Bombay Presidency. 



Bruce Foote described the Kolar schistose band as a " synclinal 

 trough resting on the adjacent granite-gneiss rocks;" 2 but although 

 it may be true that the Dharwar schists are younger than the bulk 

 of the granite-gneisses, recent work of the Mysore Geological 

 Department shows that the stratigraphical relations of the two 

 systems are obscured by a later intrusion of granite along the 

 margin of the schist belt. If reference be made to the geological 

 map (PI. 21) which is the result of the recent labours of the Mysore 

 State Geological Department, and which has been kindly placed at 

 my disposal by Mr. W. F. Smeeth, the present head of that Depart- 

 ment, it will be seen that the schist belt is invaded on both sides by 

 granitic intrusions. 



The " granite-gneiss " is divided by the Mysore Geological 

 Department into three types: (i) the grey gneiss with marked 

 banded structure and dark basic segregation veins and patches, 

 consisting chiefly of biotite and hornblende, these minerals being 

 also characteristic of the gneiss itself; (2) an older prophyritic 



1 " Report on the auriferous tracts in Mysore." Selections from the Records 

 of the Mysore Government, Bangalore. Mysore Government Press, 1887, p. 1, and 

 Rec. Geol. Surv. Ind., Vo!. XXI, p. 40, 1888 



2 Notes on a traverse across some gold-fields of Mysore. Rec. Geol. Surv. 

 Ind., Vol. XV, Part 4, 1882, p. 193. 



