352 GRENAAT KOP 



On the farms De Vrede, Portugal's Kiver, and Blaauw 

 Blommetjes Keep, in the Sutherland Division, there are 

 breccia-filled pipes and dykes. The Blaauw Blommetjes 

 Keep pipe gives off a sheet-like extension of the breccia, 

 which distinctly traverses a thick sheet of dolerite, and 

 thereby proves that the production of the vent was 

 posterior to the consolidation of the dolerite, a strong 

 confirmation of the evidence afforded by the fragments 

 of coarsely crystalline dolerite found in the breccias of 

 many of the necks of this class. 



Three small necks of a similar type occur together on 

 the boundary between Kafir's Kolk and Grenaat Kop in 

 Prieska. The breccia which fills them is almost entirely 

 composed of indurated fragments of the Dwyka series, 

 the formation through which the pipes pass, but there 

 are also fragments of an igneous rock allied to " blue- 

 ground ". Grenaat Kop itself and the ridges farther 

 south of it are composed of Dwyka shales which have 

 been considerably silicified, evidently as the result of 

 heated water ascending along certain lines of fracture 

 and brecciation in the strata, just as in the case of Salt- 

 petre Kop. This system of fissuring extends in a 

 north-north-westerly direction along the belt of altered 

 sediments, and it is noteworthy that not only are the 

 above-mentioned pipes situated along this line but there 

 are as well at least three dykes composed of blue-ground 

 and possessing a similar direction. 



A large agglomerate-filled pipe penetrates the Malmes- 

 bury beds of the Kobe Valley in Van Ehyn's Dorp ; l it 

 resembles in some respects the necks of the Saltpetre 



*G. C.,ix.,p. 41. 



