Sir J. B. Stone — The Kimherley Diamond Mines. 493 



how they came into position, and what is the precise nature of the 

 material in which they are imbedded. 



Whilst speculative theories have been propounded, which have 

 added interest to what was already a romantic story, observations 

 have been made at the same time, which are of more exact scientitio 

 value and have contributed to a larger knowledge of the subject. 

 Among the facts which have been disclosed are the following : 

 the variation of the character in the diamonds found in the different 

 mines and localities ; the varying amount and value of the " stones " 

 from the respective mines, and even from the several parts of the 

 same one ; and the variable nature of the " Blue Ground " material. 



The diamonds not only occur in all shades of colour, from deep 

 yellow to blue-white, from deep brown to light brown, in green, 

 blue, pink, orange, pure white, and at times even opaque, but also 

 they vary in shape, brilliancy, and size ; nevertheless so generally 

 uniform are the particular characteristics of those of any mine, that 

 exj)erts, it is said, can unmistakably distinguish the products of the 

 several workings. 



As an illustration, the " stones " from the Jagersfontein Mine are 

 worth thirty or forty per cent, more than those from the De Beers 

 Mine, owing to their purity of colour and brilliancy, though the yield 

 of the latter is evenly about tenfold that of Jagersfontein. Nor is 

 this feature of variation distinguished only in the " stones," for the 

 Blue Clay^ also varies in its character, it being distinctly different 

 in texture in the several workings; thus, in the De Beers Mine it is 

 so much harder than in the Kimbei'ley Mine, as to take quite twice 

 the length of time to reduce it in the process of disintegration, or, to 

 use a local word, to " pulverize " it, an operation to which all the 

 material is subjected. The yield, too, of diamond wealth is irregular 

 and singularly erratic : the west ends of both the Kimberley and 

 De Beers Mines do not pay to work, whilst the north, south-east, 

 and centres are exceedingly rich, a condition which is even more 

 apparent where the " Blue " lies in close proximity to volcanic rock. 



The disintegration of the " Blue " is an interesting process, and 

 throws some light upon the character of the material itself. In past 

 times the same formation, exposed at the surface to the action of the 

 atmosphere, became oxidized and softened, and was always known 

 as Blue Clay, and to-day similar weathering action is relied upon 

 to soften the material which comes from the deep workings in the 

 shape of hard rock. There are thousands of men busily labouring in 

 the labyrinth of galleries below, at varying depths up to 1200 feet, 

 and loads of rock are rapidly sent to the surface, quickly filling long 

 trains of Itallast trucks, which are run to the adjacent plains where 

 the wagons are tilted and the precious material is scattered over the 

 ground to undergo the process of weathering ; this in the main being 

 all that is needed to disintegrate it, that is if sufficient time is allowed. 

 Violent mechanical means of crushing or breaking up the Blue 



1 This, by the way, is not clay at all when first dislodged in the underground 

 workings, but hard rock, which has had to be "won" by means of drilling and 

 blasting, such as is customary in rock-mining operations. 



