THE BES^GEBA DIAMOND FIELD. 95 



In other parts of the ground we see a compact, rather small- 

 grained silicious brecciated conglomerate, strongly agglutinated 

 together by a ferruginous cement ; occasionally the pebbles 

 incorporated in this conglomerate are of rather large size. 



In one part of the field the junction of the conglomerate with 

 the argillaceous shale is clearly shown in the cutting formed by a 

 small gully. 



Both the shale and conglomerate beds appear to have undergone 

 much disturbance ; and at this particular spot diamonds are said 

 to be plentiful on the conglomerate but not on the shale. The 

 surface of the shale is here free from drift, but the conglomerate 

 does not appear to be quite free from it. The miners regard the 

 conglomerate as being of itself diamond-bearing, but this has not 

 been put to any absolute proof. 



Up to the present all the diamonds have been found within a 

 foot or so of the surface, in fact just at the grass roots. In no 

 case have the workings been carried to greater depths than two 

 or three feet ; in some parts examined the drift itself is not thicker 

 than that. 



In the former sinkings made by the gold diggers diamonds 

 have occasionally been met with at depths of 60 feet, or even more ; 

 but, as the men were working for gold, no great attention Avas 

 paid to the diamonds, and it is quite likely thiit they fell in from 

 the surface. 



The method employed in the search for the precious stones is 

 very simple :— The drift is stripped off and carted to the puddling- 

 machines, where it undergoes a great diminution in bulk by the 

 removal of the clay and fine sand ; the large pebbles are then 

 screened ofi", and the clean gravel remaining is passed through 

 one of Hunt's diamond-saving machines. But since this apparatus 

 depends upon the principle of separation by difference in specific 

 gravity, it does not perhaps afford the best method which could be 

 devised ; it may answer well enough for gold and other bodies of 

 very high specific gravity, but must certainly answer very imper- 

 fectly for diamonds, on account of their comparatively low specific 

 gravity, viz., 3'4 to 3'5, which is nearly equalled by most of the 

 accompanying minerals, and exceeded by some. 



I should be inclined to recommend the methods employed in 

 Africa and Brazil, since they would probably prove more 

 efficacious. 



"We may now pass on to consider in more detail the mineral- 

 ogical nature of the drift, or " wash-dirt" as it is termed by the 

 miners. 



From Messrs. Westcott and M' Caw's claims I obtained three 

 difierent specimens. See samples Nos. 1, 2, and 3. 



