Parent-Bock of the Diamond in South Africa. 99 



proved no more than the presence of garnets in the parent 

 rock of the diamond, and thus made the eclogite (abeady 

 known to occur) highly probable, for, as observed by 

 Professor E. Beck,^ the specimen itself is blue ground. 

 In confirmation of liis statement I pulverised a fragment,- 

 and find that the powder corresponds with the matrix of 

 the blue ground when similarly treated. The latest 

 discoveries enable me to complete the chain of evidence 



Eclogite Boulders contaAnivg Diamonds. 



The first named, that containing several diamonds, is a 

 fragment (perhaps from a quarter to a third) of a boulder, 

 which probably was ellipsoidal in shape, two of the axes 

 being nearly equal and the third distinctly the longest. 

 We may infer that it was rounded from a roughly rectan- 

 gular block, since the curved surfaces are slightly flatter 

 in the middle parts. The axial lengths in the fragment 

 (prior to removing a piece from one end) were approxi- 

 mately 4 in. by 3 in. by 2 in. The rock is coarsely 

 granular, apparently composed of two green-coloured 

 minerals, one darker than the other (possibly only 

 different states of a single mineral), and of rich resin-pink 

 coloured garnets, varying in size from a hemp-seed to a pea, 

 with slightly irregular distribution. The outer surface of 

 the boulder, except for a very small " step " on one side, 

 is smooth, the garnets barely, if at all projecting. The 

 latter are covered with a rather soft, dark skin, sometimes 

 slightly thicker than the thumb nail, which often has 

 partly fallen oft'. This, as can be seen on the broken 

 surfaces, becomes less conspicuous in the inner part of the 

 boulder, and is sometimes invisible to the unaided eye. 

 Two small diamonds are exposed on the curved outer 

 surface, one about half, the other about one fifth of an 



1 Ut au]>ra. 



2 I could not advise Mr. Trubenbacli to have a slice cut from the specimen, as I 

 feared It might be injured, but he kindly detached a little fragment from the opposite 

 tnd to that named above, which I have thus examined. 



