6.— SEDIMENTARY DEPOSITS IN NATAL. 

 By J. A. H. Armstrong. 



The progress of research into the resources of Natal as a gem 

 producing country has been extremely slow. There is reason to 

 believe that the geological history and mineralogical wealth of our 

 Colony is but imperfectly revealed, and thus there is still hope of 

 success. Five years have elapsed since my attention was directed 

 to the reported occurrence of gem-bearing alluvial beds in Northern 

 Natal, in the vicinity of Ladysmith. During a sojourn in that 

 neighbourhood at that time, I proceeded to the locality of the sup- 

 posed find, to satisfy my curiosity and in the interest of our 

 renowned science. The neighbouring country formations consist for 

 the most part of various dark and light coloured shales belonging to 

 the well-known Ecca series, similar in appearance and character to 

 those found outcropping at various places along the Eastern Coast 

 of Natal. These shales are frequently intruded by a dark igneous 

 basic rock, approximating in parts to a basalt, and in parts to a 

 fine-grained dolerite shewing the ophitic structure. These intrusions 

 are of a complex structure, but in some cases assume the aspect of 

 almost vertical dykes, and in almost all cases have given rise to 

 varied and well-formed distinct hills or kopjes. 



Another noticeable feature for observation is the vast number 

 of spherical, angular, subangular, and other irregularly shaped 

 boulders, which are to be found lying on the summits and slopes of 

 these kopjes. The boulders consist of the same material as 

 the intrusive dykes, and show the characteristic basaltic weathering. 

 A curious feature is observable at times, even among the largest of 

 these boulders, in their tending to split in pieces. This is produced 

 by exposure to sudden changes of heat and cold. The so-called 

 alluvial deposits are to be found in the valleys overlain by a deposit 

 of loam of varying thickness, ranging in colour from a dark grey to 

 a dark reddish colour, indicative of the presence of iron. The over- 

 lying deposit at places assumes a plastic nature, and thus verges on 

 the domain of a true clay. The line of demarcation between the 

 two series is very distinct in many places, and there can be no doubt 

 that the alluvial beds mark a distinctly different period to the over- 

 lying deposit, and could hardly lead to the conclusion that 

 the alluvial beds should be considered a portion of the subsoil, more 

 especially as the underlying rocks consist of denuded shales pre- 

 senting a marked unconformity, and thus totally unconnected with 

 the series above. The pebbles constituting the greater part of the 

 alluvial beds are of various sizes and shapes, and are often found 

 filling up the interstices of larger boulders of a basaltic or doleritic 

 nature that are visible. No garnets, carbons, ilmenite, olivines, 

 corundum, or other associate-minerals of diamondiferous deposits, 

 were observable. The pebbles consisted more or less of varieties 

 of clear quartz, feldspar, or shale fragments, which had evidently 

 undergone considerable wear from water action, and had almost likely 

 travelled some distance. The whole seemed to be uniformly distri- 



