PRE-CAPE ROCKS OF SOUTH AND WEST OF COLONY 31 



a gneiss, but this extreme stage is connected with the 

 uncrushed rock through breccias of different degrees of 

 coarseness. 



The granites of the Paarl and Stellenbosch districts 

 contain a fair amount of microcline, a variety of felspar 

 which is rare in the Saldanha Bay and Darling area. 

 On the western edge of the Bottelary mass cassiterite 

 or tinstone occurs along with wolframite and tourmaline 

 in quartz veins and also in greisen or quartz-muscovite 

 rock in a gneissose granite. 



Near Somerset West there are two masses of granite ; 

 the smaller one, Schaapen Berg, just east of the village, 

 contains some interesting varieties of rock. The main 

 mass of the intrusion is a biotite-granite with little mus- 

 covite, but the muscovite is very abundant in certain 

 places and the felspar decreases in amount, and may 

 disappear completely, so that the rock becomes a greisen. 

 In other parts tourmaline is extremely abundant, some- 

 times giving rise to schorl rock, composed of tourmaline 

 and quartz only. At other places andalusite, showing 

 a beautiful pink tint under the microscope, forms a 

 large part of a rock composed of quartz, tourmaline, 

 muscovite, andalusite, and apatite. 



The granite underlying a great part of the sandstone 

 of Table Mountain and the other mountains of the 

 Peninsula has been described by many previous writers. 

 Professor E. Cohen 1 of Greifswald has described in de- 

 tail the granite and the altered clay-slate near it, from 

 the immediate neighbourhood of Cape Town ; he was 



1 E. Cohen, " Geognostisch-petrographische Skizzen aus Sud Afrika," 

 Neites Jahr. filr Min., etc., p. 460, 1874. 



