104 Becker — Auriferous Conglomerate of the Transvaal. 



includes the northern part of the Transvaal and portions of 

 Mnshonaland and Matabeleland. Its extent is approximately 

 130,000 square miles and the remnants in it of prehistoric 

 workings are so extensive as to lead to the belief that gold to 

 the value of millions of pounds sterling has been extracted. 

 The ancients, however, appear to have been unaware of the 

 auriferous character of the banket, The age of the rocks in 

 the northerly area is uncertain but it is supposed to be Silurian 

 or older. They are known as the Swasi schists. They are cer- 

 tainly older than the banket beds, the more important of which 

 occur in the Lower Cape formation. This, by imperfect corre- 

 lation with occurrences near Cape Town, is thought Devonian 

 or Lower Carboniferous. A less important banket, the Black 

 Reef, occurs in the Upper Cape which rests unconformably on 

 the lower series. The Triassic coal-bearing series is separated 

 from that containing the Black Reef by another unconforma- 

 bility and shows only traces of gold. 



The uplift of the Lower Cape was of moderate violence and 

 took place under no great load. The northerly edge of the 

 series was sharply bent upwards and the outcrops are now 

 found at angles of southerly dip usually included between 45° 

 and 70°. To the southward, underground, the strata rapidly 

 flatten ; so that in the lower workings dips of 20° to 30° are 

 common. The bending of the beds was achieved to a smaller 

 extent by plastic flexure than by multiple systematic fractures, 

 and many of the faults are marked by dikes of subsilicic 

 pyroxenic rocks. The main period of uplift and dike injection 

 occurred before the Upper Cape. In such cases of what may 

 be called comminute flexure, the fractures though simultaneous 

 dislocate one another at the instant of formation. When filled 

 with dikes or veins they often give the erroneous impression of 

 successive disturbances. There appear, however, to have been 

 along the Witwatersrand some relatively unimportant injections 

 of later date than the main uplift. 



Associated with the dikes, and manifestly connected with 

 them genetically, are numerous quartz seams. These cut the 

 country as irregularly as the dikes. As a rule they show 

 neither gold nor sulphurets, but sometimes masses of pyrrhotite 

 and a little pyrite are found in them, and in a few cases pockets 

 of gold have been encountered, particularly, it is said, at their 

 intersection with the reefs. It is possible that this last conclu- 

 sion is an erroneous one, for the white veins nowhere contain 

 gold so distributed as to form workable ore in considerable 

 quantities, and it is only where they cross drifts or stopes that 

 they are broken down. There is no way of ascertaining just 

 how much gold has come from the pockets in the white quartz, 

 but opinions among the managers seem agreed that it does not 



