TERTIARY AND RECENT DEPOSITS 381 



The hard quartzite is at most ten feet thick, but the 

 underlying soft clayey material, into which the quartzite 

 passes without any definite break, is at places as much 

 as forty feet thick. 



The top of Kentani Hill, the only conspicuous ele- 

 vation above the general surface of the plateau that 

 stretches northwards from the Kentani escarpment, is 

 formed by a hard quartzite, vitreous in parts, but usually 

 with a rough pitted surface. The quartzite, which is 

 only a few feet thick, passes downwards into variously 

 coloured clays from thirty to forty feet thick. 



A similar siliceous rock from a farm about nine miles 

 south of Komgha village contains the silicified seeds of 

 Chara, small spherical bodies with ribs passing spirally 

 round them, and silicified shells of Limncea. This is the 

 only surface quartzite in the Colony known to contain 

 recognisable fossils, but at present nothing is known of 

 its extent. 



On the Cape Flats there are several outcrops of sur- 

 face quartzite, some of which contain plant remains 

 that have not been determined. One well-known out- 

 crop is near the main road to Stellenbosch about ten 

 miles from Cape Town, and there are several others in 

 its vicinity. The Cape Flats quartzites are usually 

 whiter and more uniform in grain than the similar rocks 

 in other parts of the Colony. The white colour is due 

 to the almost complete absence of clay and ferruginous 

 colouring matter; the quartzite passes downwards into 

 a sandstone and that again into loose sand, which is 

 identical with the white sand that occurs under the sur- 

 face soil over a great part of the Flats. 



