Vol. XI, Nos. 5 & 6.) The Geological History of S. India. 147 
[V.S.] 
belonging to the Dharwar System on account of the evidence 
of their having been cut off and broken up by the subsequent 
intrusive gneiss. They are of importance for their mineral 
contents and contain considerable deposits of iron-ore, chrome 
ore and magnesite. It is very probable that the Chalk Hills 
of Salem, which are conspicuous on account of the abundance 
of veins of white magnesite, belong also to this series. 
Finally we have some large intrusive masses of diabasic 
or dioritic character which appear to be later than many of 
the rocks already mentioned, but prior to the gneiss and so 
regarded as of Dharwar age. 
At the close of the Dharwar age the whole of Southern 
India was covered with a mantle of these Dharwar rocks 
granites to become a very uneven one. Subsequent denuda- 
tion for many millions of years removed the greater portion of 
the mantle of Dharwars, with the result that we now see the 
underlying granite and granitic gneisses exposed at the 
surface e comparatively narrow strips of the Dharwar 
schists which still remain are but the deeper fragments of the 
once thick, continuous layer. 
ith this brief notice of the Dharwar System we may 
Pass on to the subsequent granites and gneisses which now 
occupy by far the greater part of the whole area. ‘ 
_ The earliest of these is a comparatively fine-grained 
micaceous gneiss with bands and veins of coarser granite, 
vials bu 
including the banded ferruginous quartzites. This gneiss was 
t recognized as a wide band near the eastern edge of the 
i 
zed in the deeper workings of the Mysore mine a mile 
te ao a0, the north of the shal The oii is often charac- 
pea by the presence of grains or blebs of opalescent quartz, 
aa varying from a slight bluish milkiness to brown or 
As grey, and has been referred to as opalescent-quartz gneiss. 
a less cumbersome name and on account of its intimate and 
oh ly genetic connection with the auriferous veins of the 
4mpion lode of the Kolar Goldfield, I propose to call it, 
