TJie Parent-rock of the Diamond in South Africa. 225 



Prior to the discovery, just mentioned, one or two instances had 

 occurred at the De Beers Mine of a diamond apparently enclosed by 

 or projecting into a pyrope. One such, the garnet being the size of a 

 rather large pea, is in the collection at Freiberg (Saxony), to which it 

 was presented in 1892.* 



The specimen foimd by Mr. Trubenbach at the Xewlands mine, was 

 a piece of blue ground, with a pyrope projecting from one angle. 

 A small, apparently broken, diamond seems embedded at the top. 

 The others (five) are well crystallised, two on one side, three almost in 

 contact on the other. The pyrope (which has a kelyphite rim) seems 

 to be indented by two, but to have once included the others, as they 

 are in contact with the unaltered mineral. We were thus brought so 

 far as to associate the diamond with the pyrope ; though this proved 

 no more than the presence of garnets in the parent rock of the diamond, 

 and thus made the eclogite (already known to occur) highly probable, 

 for, as observed by Professor E. Beckf, the specimen itself is blue 

 ground. In confirmation of his 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 containing 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 dis- 

 tinctly the longest. AYe may infer that it was rounded from a roughly 

 rectangular 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 approximately 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 off. 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. 



* A. W. Stelzner, ' Sitzungber. der Isis zu Dresden,' 1893, s. 85, and K. Beck, 

 'Zeitsch. fur praktische Geologie,' 1898 (May), p. 163. 

 f Vt sujpra. 



X I could not advise Mr. Trubenbach to bare a slice cut from tbe specimen, as I 

 feared it might be injured, but he kindly detached a little fragment from tbe oppo- 

 site end to that named above, -which I have thus examined. 



