DETAILED DESCRIPTIONS OF ROCKS. 73 



Several dykes of dolerite run through the rocks, traversing both the 

 quartzites and the granite veins. The largest of these occurs in a 

 ravine at the north-east corner of the village ; the rock is coarse 

 grained and a good deal decomposed, forming a dyke about 12 feet 

 wide striking north and south. A few yards up the ravine it sends off 

 a branch to the north-west. Several granite veins occur in the same 

 ravine, cutting across the strike of the quartzites and in turn cut 

 through by the dolerite. 



The whole of the northern portion of the large mass of hills 

 between Sanderao and Erinpura, extending from near Khadalo station 

 on the Rajputana-Malwa railway to the Joai river, about five miles 

 below Erinpura, consist of dark colou;ed Aravalli schists with bands 

 ofquartzite. The strike varies between north-north-east, south-south- 

 west, and east-north-east, west-south-west, but is generally in the latter 

 direction. Over the low ground to the south of these hills an exceed- 

 ingly coarse granite crops out, forming low hummocks scattered over 

 the plain, and occasionally rising to a greater height, as in the hill at 

 Khidara and in the long ridge to the south of this village running 

 parallel to the road. This rock is not often seen in contact with the 

 schists, but where it is visible the junction is very irregular, and the 

 granite sends off veins among the schists and includes fragments of 

 them. As at Sanderao the granite near the boundary is generally 

 strongly foliated, and the veins which traverse the schists are some- 

 times contorted, showing that the granite must have been injected 

 before the folding of the schists took place (PI. IV, fig. 2). This 

 granite is therefore far older than the granite associated with the Malani 

 rhy olites to the north and west. It also differs from that granite lithologi- 

 cally, being exceedingly coarse grained and containing crystals of 

 whitish felspar often three inches or more in length. Among these hills 

 a few d\kes were met with, generally running in a west-north-west, 

 east-south-east direction or at right angles to the strike of the schists, 

 and traversing both these and the coarse granite. 



'1 his granite also forms the large hills to the east of Erinpura Road 



( 73 ) 



