TERTIARY AND RECENT DEPOSITS 377 



and are like the waterworn pebbles to be found in the 

 modern stream beds. These fragments are embedded 

 in a matrix that varies very greatly ; in the bulk of the 

 rock the matrix is a sandy material, but slightly hard- 

 ened, from which the pebbles may be easily broken out ; 

 in other cases the matrix is deeply coloured by hydrated 

 iron oxide, and the rock is in consequence reddish brown. 

 Such ferruginous gravels are well developed near Gena- 

 dendalin Caledon and at the foot of theZwart Euggens 

 in the Western Karroo. Near the village of Napier there 

 is a conspicuous kopje formed of a dark, highly ferrugin- 

 ous conglomerate, which probably belongs to the same 

 gcoup of gravels that are developed to the west of the 

 village, at a considerable height above the bed of the 

 Eland's Kloof River. The ferruginous cement has in 

 many cases hardened the gravel to such an extent that 

 the rock breaks across pebbles and matrix alike when 

 struck with a hammer. 



There is a gradual passage laterally from these ferru- 

 ginous gravels to the fine-grained ferruginous rocks that 

 lie farther from the mountains, and which often contain 

 a few angular or subangular pieces of white vein-quartz 

 derived from the slaty Bokkeveld or Witteberg beds 

 underlying them. Magnificent examples of these hard- 

 ened alluvial deposits are to be found in many parts of 

 the Ruggens, forming rough-looking caps on the higher 

 hills, such as Klaas Kaffir's Heuvel near the road from 

 Swellendam to Bredasdorp. 



The ferruginous rock is often directly underlain by 

 white and yellowish clays, bleached by the slow removal 

 of the iron they once contained which is now concen- 



