68 Report S.A.A. Advancement of Science. 



rivers, consists of a series of quartz bodies in a particularly distinctly 

 laminated layer of chloritic schist. The quartz bodies are lenticular 

 in horizontal section, but are apparently elongated in depth, 

 resembling crooked, flattened columns. No doubt the reef follows 

 a line of shearing parallel to the foliation of the schist. The Phoenix 

 Reef, lower down the Tugela, is similar in character to Household's, 

 but the casing is a coarser hornblende schist. The Enterprise Reef, 

 at Nondweni, so far as it has been opened, consists of one large lens 

 of dark bluish glassy quartz as much as 26 feet thick at one place. 

 It has been driven along for a distance of 740 feet, which is probably 

 almost the full length of the lens. It appears most probable that 

 the reef lies along a line of shearing which has been opened by 

 subsequent end pressure on the strata. The Sisters Reef at Nondweni 

 is of a different type, lying as it does along the under side of an 

 interbedded basic dyke. Most of the quartz veins in the schists 

 appear to owe their origin to the opening of the folia of the schists, 

 by either end pressure or folding. 



What is known as the " Sisters Hill formation " is of special 

 interest to the geologist. It crops out as a great bed or vein in the 

 schists, with a width at one place of as much as 120 feet, and con- 

 sists mainly of silica and carbonate of iron, with some chlorite. 

 Numerous small and irregular quartz veins, many of \vhich are rich 

 in gold, ramify through the body, converting it into a " stock werke." 

 Though the unweathered rock is extremely hard, it weathers very 

 rapidly, leaving a network of quartz veins standing. 



Witwatersrand Series. — The strata which I believe belong to 

 the Witwatersrand series are exposed (i) in the Buffalo Valley, a 

 short distance above its junction with the Tugela ; (2) in the upper 

 portion of the Insuzi Valley, in the Umhlatuzi Valley, near Nkandla, 

 in the valley of the Pongola River, near Paulpietersburg and 

 Louwsburg, and in a few smaller areas elsewhere. 



The series consists, in the Colony, of alternating beds of 

 quartzite and schist with occasional beds of gold-bearing con- 

 glomerate. The beds are invariably much folded, with the axes of 

 the folds running approximately east and west. The reasons, apart 

 from authority, leading me to place the beds in the Witwatersrand 

 series, are : — 



1. The relation to the Swaziland schists which frequently 

 underlie them, and to the Table Mountain sandstone and Dwyka 

 conglomerate which in different places overlie them directly, but 

 unconformably. 



2. Their petrological character. 



3. The absence of granite intrusions. 



4. The presence of dykes exactly similar to the older dykes 

 on the Witwatersrand. 



5. The presence, in the lower portion of the series, of beds 

 containing much magnetite and similar in character to the 

 Hospital Hill shales. 



