74 Report S.A.A. Advancement of Science. 



drawing an imaginary line connecting all the sites of these pipes in 

 the various Colonies, I formed the opinion that it would not be at 

 all unlikely to find diamondiferous pipes within Natal, and that a 

 line of weakness may exist in Natal, extending from the Matatiele 

 to the Transvaal. Since then, however, I am more inclined to think 

 that, although there is every possibility of finding a diamondiferous 

 pipe some day within Natal, yet the greater probability is that a 

 fissure will be found extending along such, if any, line of weakness. 

 This view, I think, is supported by the occurrence in many Natal 

 rivers of garnets of the precious varieties, which could not in all 

 instances have been derived from granitic or gneissic formations or 

 eclogite, seeing that the existence somewhere of such a formation, 

 as I have explained, is likely, within the depths of the earth. At 

 the spot where I encountered the stuff first, I discovered small 

 pieces of a hard, brownish rock, of a flinty nature, which possibly 

 may have been a kind of porcellanite derived from the baking by 

 excessive heat of the neighbouring shales around an intrusive mass 

 of igneous rocks. These pieces gave me an impression, that it is 

 possible in areas where Ecca shales have been intruded by granitic 

 rocks of comparatively recent date, that in the vicinity of the granitic 

 bosses they have suffered so much from the intense heat and enormous 

 pressure, that minerals may have crystallised out in the baked shales, 

 such, for instance, as diamonds, the carbon being derived from the 

 shales themselves. One of the small pieces found by me contained 

 a well formed crystal of garnet, of the variety pyrope, as well as 

 quartz crystals zircon, in the form of a perfect crystal of the 

 tetragonal system, as well as a pure transparent diamond of the cubical 

 form. This leads to the conclusion that diligent search for gems 

 should be made in the Ecca shales, in those places surrounding large 

 granitic bosses, or other large bosses of igneous rocks, are intruded. 



Another series of sedimentary deposit, that is worthy of atten- 

 tion, is one which covers a considerable area in Southern Natal. It 

 appears to have been formerly some kind of clayey deposit, which 

 was full of ilmenite, olivine, and a bronze coloured mica, and which 

 has been converted into a clay srhist through pressure. The ilmenite 

 and mica are most conspicuous, and give the strata a laminated 

 appearance. One noticeable feature is the peculiar manner in 

 which it is ramified in all directions by small veins or leaders of 

 igneous rocks, and also that in places it contains at times one or 

 more seams of quartzite of an extremely white colour. Some of the 

 intrusive veins are typical graphic granite or pegmatite, the quartz 

 crystals being marked by their purity and transparency, and 

 the felspar being white orthoclase, both minerals having 

 crystallised together, and assumed forms resembling the Hebrew 

 characters. No gold has been observed by me in any of the leaders, 

 but in this schist the tale is different. Near the locality where the 

 discovery of diamondiferous deposit above mentioned was made, this 

 clay schist is also found outcropping, and small patches in it, thought 

 to be leaders, had been worked for gold some 25 years ago by early 



