V 

 Sir J. B. Stone — The Kimherley Diamond Mines. 495 



of saltpetre crystals. A more minute and careful examination 

 discloses the interesting fact that many, if not most of the stones, 

 are fractured, and are but parts of perfect crystals. Tliis indicates 

 that they have been subjected to mechanical forces, explosive or 

 otherwise, and of itself seems to prove that the diamonds were not 

 formed at the spot where they were found. 



It should be stated that above the diamond-bearing rocks there 

 are extensive beds of carbonaceous shales, and it has been supposed 

 that chemical action, due to steam generated in the volcanic rock, 

 formed the diamonds.^ Of coui'se due weight must be given to 

 the facts adduced by those who favour the idea that the diamonds 

 were actually formed at or near the spot where they were found, 

 particularly the one singular fact of the prevailing similarity of 

 stones in localities, which it is admitted remains at present unex- 

 plained ; but even if the broken diamonds were not sufficient 

 evidence, certainly the schistose surfaces of the " snake " (a hard 

 intrusive porphyritic rock), and the glossy appearance of the crater 

 face lying in contact with the Blue Ground, should be perfectly 

 convincing. 



No doubt some such chemical action as indicated did take place 

 and produced the diamonds, but it is more than probable that 

 this occurred far away from their present resting-place, the exuding 

 mud-flow having been propelled forward by earth pressure, or some 

 other dynamical force, and that the diamonds were fractured by 

 extreme pressure in transit. 



In conclusion, it is interesting to have to report that the De Beers 

 Company are energetically continuing the work of sinking in the 

 main shaft, which, it may be well to state, is through the adjacent 

 hard rock and within a short distance of the crater funnel of the 

 mine proper. This, to get to the 1200-feet level, has passed 

 through the upper beds of basalt and black shale, through the 

 hard amygdaloidal melaphyre deposit, through some 400 feet of 

 quartzite, and into the lower shale beds.'^ 



' It may be ■well here to quote a passage from a letter on this subject received 

 from Mr. W. Moses, the able director of the De Beers Mines, who ventures upon 

 a more elaborate explanation. He says : "I am inclined to stick to my theory of 

 the formation of diamonds and the depositing of them in the present formation of 

 Blue Ground or volcanic mud. To put it as short as possible, the diamonds were 

 produced from carbonic acid gas xmder extreme pressure and changes of temperature, 

 the oxygen being consumed by the carbon, etc., the result being the diamond. To 

 revert to the present deposits : they were made in the crater of an extinct volcano, 

 into which came thermal springs, which washed away the sides of the soft strata below 

 (the volcanic rocks forming the volcanic mud of the Blue Giound), and the diamonds 

 were introduced from below by the action of the boiling energy of the thermal 

 springs. The blue ground or mud, if you remember, we concluded had not gone 

 under any great heat, as the small particles of shale clearly indicated; in short, 

 the diamonds were separately formed, and were brought into their present position 

 from below." It has also Ijeen supposed, and with some show of probability, that 

 with the opportune presence of carbon, under conditions of intense heat and 

 perchance pressure, crystallization took place, the colours of the stones varying as 

 they were affected by the presence of metals or oxides of metals. 



- A letter recently received from Mr. W. Moses states that "the sinking of our 

 main shaft still continues in the blue metamorphic shale, and no change has yet 



