880 E. J. DUNXS FURTHER NOTES OX THE 



Now that the -mines are well opened out, they disclose a form less 

 circular than at first they appeared to possess. 



Kimberlcy Mine is elongated in an E. and W. direction, De Beer's 

 in a X.W. direction, and Du Toit's Pan in a S. direction (towards 

 Bultfontein, with which it may be connected by a fault). Sufficient 

 work has not yet been done to prove the extension of these elon- 

 gations for any considerable distance ; but present appearances sug- 

 gest that the first effect of the disruptive force was to cause a rent 

 in the rocks, and that the sides of this rent were torn away in the 

 weakest part by the intrusive rock until the present form resulted. 



In a few places mining-operations have pierced through the 

 "floating shale" so abundant in the southern portion of Du-Toit's- 

 Pan Mine ; and the usual soft rock is met with below. 



Under extensive areas of shale, the depth at which the dark 

 compact rock occurs is less than where no such protection exists ; 

 this would lead to the inference that the "cores" or f e pipes" have 

 decomposed from the surface downwards, and that, in all probability, 

 the rock will become more compact and less altered as depth is 

 gained. 



In all the mines the dark-coloured and less-decomposed rock 

 occurs at depths varying from 80 to 100 feet from the surface, and 

 always nearer the surface at the sides than at the centres of the 

 " pipes." 



At a depth of 120 feet, in Kimberlcy Mine, several small fresh- 

 water shells were discovered in what appears to be undisturbed 

 material. A specimen of mineralized charcoal was unearthed in the 

 same claim. 



Mode of Working. 



At Kimberley the ground is picked and blasted at the bottom of 

 the mine (a huge pit about nine acres in area, according to recent 

 surveys), broken into small pieces, and brought to the surface in 

 buckets running on wire ropes that stretch from the brink of the 

 pit to each claim ; on reaching the surface the tough decomposed 

 rock is spread on the ground and exposed to atmospheric action, 

 water being occasionally sprinkled over it to assist disintegration ; 

 subsequently it is dry-sorted (with sieves) by the old method, or, 

 what is much more efficacious, washed. 



The usual machines used for washing are : — (1) a small description 

 of puddling-machine, specially adapted for this work, as the material 

 cannot be reduced and run-off as slime or " sludge," but must be 

 got rid of in fragments about the size of disintegrated granite (this 

 process gives good results) ; and (2) a trough, with cross ripples,' and 

 rakes moving from side to side : the puddled material, with sufficient 

 water, flows through it, leaving the heavy substances at the ripples ; 

 results uncertain, but still superior to the dry method. 



The heavy sand obtained by the above processes, consisting mainly 

 of garnet and ilmenite, with the diamonds, is taken from the 

 machines and washed in sieves, in the same manner as tin-ore is 

 separated from iron-sand &c. ; and the diamonds are picked out. 



