760 H. A. BROUWER 



there to Saulspoort [369] the syenites form the periphery of the 

 complex; to the south, along Ruigehoek [326], Vogelstruisnek 

 [602], and Palmietfontein [567], they form a nearly interrupted 

 series of bare, low hills. In the southern part, near the road from 

 Rustenburg to Saulspoort [269], steep lujaurite hills rise from the 

 flat norite country. In the southeastern part, where the Rhenoster- 

 spruit leaves the hills, we again see the bare, red syenite hills on 

 both sides of the stream. Along the eastern boundary they are 

 covered by effusive rocks. The syenites are found also in the 

 central parts of the complex; in the southern part of Driefontein 

 [888] numerous hills consist of these rocks. They form a conspicu- 

 ous feature and from a distance can easily be distinguished from the 

 rounded, bare, felsite ridges. We find them also in the south- 

 eastern part of Welgeval [749], on Nooitgedacht [748], Buff els- 

 kloof [219], Leeuwfontein [429], Buffelspan [585], and Houwater 

 [496]. Near the houses on Nooitgedacht [748], in the valley of a 

 small rivulet, light syenitic rocks with white feldspars occur, which 

 are similar to some varieties of the rocks on Leeuwfontein [320] in 

 the Pretoria district. 



By transitions these rocks are connected with the nepheline 

 syenites, as well as with the effusive rocks. 



Diorites : As intimately associated with the f oyaites and 

 lujaurites, Humphrey 1 mentions the occurrence of diorites, which 

 have their greatest development in the northern part of Boeken- 

 houtfontein [889]. They are also exposed on the summit of the 

 mountain to the southwest of the native stadt on Saulspoort and 

 are found as a dike cutting through the norites on Tusschenkomst 

 [446] to the north-northwest of the Pilandsberg complex. The rock 

 is fine grained, has a gray color, and consists principally of augite 

 and labradorite. 



Effusive rocks: In my previous paper 2 it has been stated that 

 porphyritic and dense equivalents of the syenites and nepheline 

 syenites have a great development in the Pilandsberg complex. 

 Flow structure is often beautifully developed in these rocks. 



1 "The Geology of the Pilandsberg," Annual Report of the Geol. Survey of South 

 Africa, 191 1, p. 84. 



2 Oors prong en samenstelling der Transvaalsche Nepheliensyenieten, p. 16. 



