148 C4. T. pinoK. 



and diallage in the " diallage-norites" of Zwartkoppies, 

 north-east of Pretoria, described by Henderson.^ The olivine 

 in the present rock occurs in large amount in irregular 

 sections, only one or two of the larger ones showing traces of 

 prism faces. Some of the sections show curious inclusions of 

 iron-ore, consisting of minute bundles of radiating rods, 

 of which those directed parallel to the vertical axis of the 

 olivine are much more elongated than the rest. Almost 

 precisely similar characters to those of this rock from the 

 Umqueme Range ai^e presented by a rock (190) from "pieces 

 of quern," to the north of the mouth of the Umhlali River, 

 Natal. Of olivine-free rocks a diallage-norite (458) "intru- 

 sive betAveen granite and Table Mountain sandstone " on the 

 Madengela Ridge, east of Nkandla, Zululand, is noteworthy, 

 since it resembles closely the rocks from the Transvaal, 

 described by Henderson, to which reference has just been 

 made. In this rock the orthorhombic pyroxene is faintly 

 pleochroic from nearly colourless (with a very faint greenish 

 tint) to pale pink, and is enclosed and intergrown with a 

 diallage-like augite showing the well-known " herring-bone " 

 structure. 



Of finer-grained ophitic and sub-ophitic dolerites like those 

 described in the preceding section, but containing enstatite in 

 small amount in addition to augite, may be mentioned speci- 

 mens from the same locality as the above coarse-grained 

 norites, viz. north of Dingatuli Hill in the Umqueme Range, 

 and also specimens from a sill in shales north of the mouth of 

 the Umhlali River, Natal, and from a " hill north of the 

 Umhlatuzi Crossing above Middle Drift," Zululand (426). 

 In the latter rock the phenocrysts of enstatite are surrounded 

 by a sharply defined zone of augite (see PI. Y, fig. 2). 

 A chemical analysis of the last-mentioned rock gave the 

 following result under I : — 



^ 'Norites, Gabbros and Pyroxenites and other South African Rocks,' 

 London, 1898, pp. 14' and 18, and pis. iii and iv, figs. 15-18. 



