362 OCCURRENCE OF THE DIAMOND 



crystallised diamonds in the garnets of an eclogite from 

 the Newlands Mine indicated that the gem was a prim- 

 ary constituent of certain holocrystalline rocks which 

 are in all probability deep seated. 



Since then diamonds embedded in single garnets or 

 in the garnet of an eclogite have been found in several 

 other mines, and the views of Prof. Bonney 1 have thus 

 received considerable support. 



Diamonds have not yet been found in the Iherzolites 

 or other ultrabasic rocks of South Africa, and it is doubt- 

 ful whether such rocks are at all closely related to the 

 eclogites. The diamond has, however, been discovered 

 in a peridotite plug or boss in Arkansas 2 and in a dia- 

 base dyke near Inverell in New South Wales ; a whether 

 the gems crystallised out of the material in which they 

 were found, or whether they were derived from some 

 deep-seated rock cannot yet be decided. 



It seems not unlikely that the diamonds found in the 

 blue-ground have reached the places where they are 

 found owing to the explosive disruption of certain dia- 

 mond-bearing rocks, some of which were eclogites. 

 The frequent occurrence of portions of fractured dia- 

 monds in the breccia is noteworthy as indicating that 

 the gems did not crystallise from the molten magma of 

 kimberlite. 



There is great variation in the character of the stones 



1 T. G. Bonney, G. M., 1899, p. 309. 



2 G. Kunz and H. S. Washington, Trans. Amer. List. M. E., No. 20, 

 1908, p. 187. 



' A T. W. Edgeworth David, Congrte Gfoloq. Internal, p. 1201, 1906, 

 Mexico. 



