206 THE GENESIS OF THE DIAMOND, 



and allied to eclogites. At a meeting of the Royal Society '^ he pre- 

 sented his conclusions : 



The blue groimd is not the birthplace either of the diamond or of the gar- 

 nets, pyroxenes, olivine, and other minerals, moi-e or less fragmental, which it 

 incorporates. The diamond is a constituent of the eclogite, just as much as a 

 zircon may be a constituent of a granite or a syenite. * * * i ij^d always 

 expected a peridotite (as supposed by Professor Lewis), if not a material yet 

 more basic, would prove to be the birthplace of the diamond. 



Can it possibly be a derivative mineral, even in the eclogite? Had it crys- 

 tallized out of a more basic magma, which, however, was still molten when one 

 acid more was injected and the mixture became such as to form eclogite? 

 But I content myself with indicating a difficulty and suggesting a possibility ; 

 the fact itself is indisputable that the diamond occurs, though rather sporadic- 

 ally, as a constituent of an eclogite, which rock, according to the ordinary rules 

 of inference, would be regarded as its birthplace. 



Professor Bonney's statement that diamonds occur in the eclogite 

 of the Newlands mine caused me to examine the eclogite which is 

 foimd in all the mines at Kimberley and has always been treated as 

 Avaste rock and thrown away. There are tons of it lying about the 

 Kimberle}^ mines. I have examined hundreds of pieces of this rock, 

 but never foimd a diamond, nor have I ever heard of a diamond 

 being found in it by anyone during the many years that these fields 

 have been worked. I caused about 20 tons to be collected and sent 

 to a test plant, where it was crushed and afterwards jigged, but it 

 contained no diamonds. Surely if one could find diamonds in the 

 eclogites of a poor mine like the Newlands, the total diamond yield 

 of wdiieh was only a few hundred carats, one would naturally expect 

 to find them in the eclogites from mines in the vicinity of Kimberley, 

 which are so rich. 



Mr. Waldemar Lindgren, who is connected with the United States 

 Geological Survey, has had an opportunity of studying the blue 

 ground and the minerals contained therein from samples supplied by 

 the writer from which 45 slides were made. His conclusions are as 

 follows : 



In looking over the literature [on diamonds], especially the papers by Profs. 

 A. W. Stelzner and T. G. Bonney, it seems to me that the connection of the 

 diamond with the garnet in the peridotite and pyroxenite has been satisfactorily 

 proved. It is not possible to regard it as formed in the "blue ground." On the 

 contrary, it was evidently contained in the peridotite magma and crj'stallized 

 with it. 



A specimen of the rock, which I presume to be similar to the 

 eclogite spoken of by Professor Bonney, taken from Dutoits2:)an mine, 

 was handed to Dr. G. F. Becker, who had a slide made from it. He 

 determined the rock to be Iherzolite, and says : 



a Proceedings of the Royal Society, Vol. LXV, July 27, 1S99. 



