PRK-CAPE ROCKS OF THE NORTH OF THE COLONY 65 



present. The structure varies from massive to gneissose, 

 and there are frequently alternations of the two types. 

 The gneissose arrangement is not the result of earth- 

 movements subsequent to the consolidation of the rock, 

 for autoclastic structures are rare ; the parallelism must 

 have been caused by movements in the magma before 

 and during its consolidation. Porphyritic varieties are 

 infrequent. Pegmatites and quartz veins, on the other 

 hand, are abundant. 



In the Maf eking Division the granite contains in- 

 clusions of various schistose and granulitic rocks which 

 represent portions of an older formation. Those in- 

 clusions are rich in hornblende and sometimes contain 

 augite, epidote, and garnet. They recall fragments of 

 the Marydale (Kheis) beds enclosed by the granite of 

 Prieska, and are probably of the same nature. 



In Prieska, Kenhardt and Gordonia there are large 

 tracts of granite and gneiss west of the hills made of 

 the Transvaal formation ; small areas are found to the 

 east of these rocks as well, in the valleys tributary to 

 the Vaal River and the inlier crossed by the Brak River 

 at T'Kuip. As in the case of the northern districts, the 

 granite is often covered with sand and rarely forms 

 ridges. A prominent little "tor" occurs just outside 

 Prieska Poort and another is the Water Kop on Jackals 

 Water ; near Upington and at Put Zonder Water there 

 are kopjes made of huge rounded boulders, the kernels left 

 by the weathering of the granite along joints. These 

 granites contain microcline in considerable quantities 

 and are often gneissose ; they resemble the Bechuana- 



land rock. On the south-west flank of the Doornbergen 



5 



