762 H. A. BROUWER 



found the effusives to form a thick capping resting upon the red 

 syenites. The effusive rocks are found in the northeastern part 

 of Buffelspan [585], in the high ridge from Houwater [496] to Wijd- 

 hoek [701], and appearing again at the other side of the Rustenburg 

 road, where the effusives of the ridge are in contact with lujauritic 

 rocks and can be followed in a northwesterly direction. On Tus- 

 schenkomst [331] and Welgeval [749] they are separated from the 

 lujaurite by a shallow valley at the contact. Still more to the 

 north we find the effusive rocks on Schaapkraal [12] and on Driefon- 

 tein [888], where they are exposed in the valley of a rivulet, which 

 flows in the direction of Rooderand [399]. On the northern farms 

 of the Pilandsberg the high ridges of effusive rocks bend around 

 parallel to the circumference of the complex; on the western farms 

 they have their greatest development and almost entirely hide the 

 deep-seated rocks. 



The rocks of the country around the Pilandsberg. — The rocks 

 which surround the Pilandsberg complex are the norites and 

 granites of the Bushveld igneous complex and the quartzites and 

 shales of the Pretoria series. 



Norites and Pyroxenites: These rocks form the characteristic 

 small hills (Pyramids, Zwartkoppies) parallel to the Magaliesberg 

 range. They bend to the northwest in the neighborhood of 

 Rustenburg, but the characteristic hills disappear long before they 

 reach the Pilandsberg; much more to the north, on the farm 

 Modderkuil [565], we see them again just in the continuation of 

 those to the south of the Pilandsberg. The bands of magnetite 

 are found to the southeast of the Pilandsberg. They end against 

 the red syenites near the boundary of the farms Rhenosterfontein 

 [867] and Rhenosterspruit [90.6], but are found again to the north 

 of the Pilandsberg. We see that the whole southern part of the 

 Pilandsberg is immediately surrounded by the basic rocks; on 

 the farms Ledig [744] and Koedoesfontein [818] they are in imme- 

 diate contact with lujaurites and allied rocks. Near the boundary 

 of Zandrivierspoort [747] and Mahobieskraal [562] the isolated 

 hills of aegirine-amphibole foyaites and the ridges of Magaliesberg 

 quartzite come close together. At a small distance farther to the 

 northwest and to the west the basic margin of the Bushveld com- 



