NOTE OX KIMBERLITE FROM THE BELGIAN 



CONGO. 



By P. A. Wagner, Ing.D., B.Se. 



Read July 17, 1920. 



Some thirty vSeparate occurrences of kiniberlile have so 

 far been discovered in the Katanga division of the Jielg'ian 

 Congo. The majority of these are situated on the Kundelungu 

 Plateau, but there are also several occurrences in the foothills 

 by which the plateau is flanked on the east, and at least two 

 occurrences on the plains between the plateau and the Luapula 

 Biver. These plains have a mean elevation of between 

 3,200 and 3,400 feet above sea-level, wliile the altitude of 

 the plateau ranges from 4,500 to wpU over 5,000 feet. The 

 country rock in every instance is red felspathic Kundelungu 

 sandstone, correlated by Studt* with the Pietoria series of the 

 Transvaal system. 



In a previous reference! to the deposits the writer 

 distinguished between {a) the Eastern Kundelungu Group, that 

 includes about twenty occurrences arranged in a curved line 

 intersecting at an acute angle the eastern edge of the plateau, 

 and {h) the Western Kundelungu Group, including twelve 

 occurrences situated near the western edge of the plateau. 



All of these occurrences, which comprise pipes, chonoliths 

 and dykes, have by this time been thoroughly tested, and 

 while some have been found to carry diamonds of good cjuality, 

 none of them appear to be worthy of exploitation. The largest 

 diamond found weighed 6 carats. The average weight of the 

 stones recovered is stated to liave been about one-sixth carat. 



The kimberlite appears throughout to be of the basaltic 

 variety, and we are here clearly dealing with a province of 

 basaltic kimberlite, the precise limits of which have yet to be 

 defined. 



The pipes and dykes yield the same assemblage of minerals 

 as the kimberlite occurrences of South Africa, and some of 

 them are rich in nodular xenoliths of the cognate type. 



Studt, J who published, in 1912, an interesting description 

 of the Eastern Kundelungu Group, was the first to remark on 

 the similarity between the kimberlite of certain of the occur- 

 rences ajid that of the Kimberley mines. This the writer 

 was able to confirm by microscopic examination in the case 

 of the " hardebank " of the Kambeli pipe,§ situated on one 



* Geol. Soc. S. Africa, 1913, pp. 44-106, Table I. 

 t 67. "' The Diamond Fields of Southern Africa," pp. 102-103. 

 X Cf. Studt, F. E. : " Report on Kundelungo Pipes, Tanganyika 

 Concessions, litd." 



§ Lnr. rif., p. 103. 



