468 GEOLOGY OF CAPE COLONY 



the ore pockets have apparently been formed by con- 

 centration of the metallic sulphides in certain parts of 

 the intrusions. This view was put forward by Wyley 1 

 as long ago as 1856 and has been confirmed by Schenck 

 and other observers subsequently. The dykes are 

 either poor or barren along considerable portions of 

 their lengths, and Kuntz 2 has noticed that the ore- 

 pockets are frequently located just where the formations 

 are crossed by west -north- westerly breaks, or where the 

 adjoining gneiss contains layers rich in iron. 



There are many smaller mines in this neighbourhood 

 which are being worked on a very small scale, while 

 abandoned workings are numerous in the area known 

 as the Eichtersveld enclosed by the big bend of the 

 Orange Eiver in the extreme north of the district. 



At Areachap, a little west of Upington, a copper lode 

 has recently been opened out, the enclosing formation 

 being the Kheis quartz-schists. Quartz veins carrying 

 copper are present in various parts of Hay, Gordonia 

 and Prieska in the same and in younger formations. 



In the Mount Ayliff district in East Griqualand 

 copper-pyrites and pyrrhotine have been found along the 

 junction of the Karroo sediments with the great mass 

 of intrusive dolerite forming the Insizwa Mountain. 

 The ore is reported to be confined to the lowermost 

 part of the dolerite, and may possibly be, as in the 

 Namaqualand occurrences, a constituent of the igneous 



1 A. Wyley, Report upon the Mineral and Geological Structure of 

 South Namaqualand, etc., Parliamentary Report, G. 36, Cape Town, 

 1857, p. 30. 



2 J. Kuntz, T. S. S. S. A., vii., p. 70. 



