﻿140 



PROP. P. DAWSOM^ ADAMS ON THE 



[May 1908 



One of the most interesting and important groups of rocks in the 

 area is that consisting of the nepheline- and associated alkali- 

 syenites. These rocks are, as a rule, light in colour and coarse in 

 grain, and generally show a more or less distinct foliation which 

 coincides in direction with that of the surrounding rocks. The 

 rock in places displays a remarkable coarseness of grain, passing 



into nepheline-syenite-pegmatite, in which masses of nepheline a 

 yard in diameter may be found. The rock, furthermore, in the 

 north-eastern portion of the area presents the phenomenon of a 

 magma supersaturated with alumina, from which the excess of 

 alumina has separated out in the form of crystals of corundum. 

 These corundum-bearing syenites have been made the basis of an 

 extensive industry, being worked for corundum on a large scale at 



