224 



Prof. T. G. Bonney. 



eclogite.* As to the genesis of the diamond, more than one opinion 

 has been expressed. Professor Lewis regarded the matrix as a porphy- 

 ritic form of peridotite, once a lava, now serpentinised,f in which the 

 diamond had been formed by the action of the molten rock on some 

 carbonaceous material (probably the Karoo shale). Others regarded 

 the matrix as a true breccia, comparing it with the agglomerates in 

 volcanic rocks. But among the latter, some thought that the diamond 

 had been produced in situ by the action of steam or hot water in a 

 subsequent solfataric stage of the volcano, while others (including 

 myself) held that it had been formed, like the garnets, pyroxenes, &c.,. 

 in some deep-seated holocrystalline mass which had been shattered by 

 explosions.]: 



The specimens which I am about to describe were obtained at the 

 Newlands Mines, West Griqualand ; from 40 to 42 miles from 

 Kimberley, almost due N.W. Here the workmen occasionally came 

 across well-rounded boulder-like masses of rather coarsely crystal- 

 line rock, studded with garnets, which are sometimes about a foot 

 in diameter. Specimens of these were found or obtained by Mr. G. 

 Tmbenbach, the London manager of the Newlands Diamond Mine 

 Company, during a visit to the mines in 1897. His interest had 

 already been aroused by picking up a specimen, presently to be noticed, 

 in which some small diamonds occurred, very closely associated with 

 a garnet ; so the boulders were brought back by him to England. On 

 careful examination a small diamond was detected on the surface of one 

 of these. On breaking the boulder others were revealed. The most 

 interesting fragment was sent by Mr. Tmbenbach to Sir W. Crookes, 

 who showed it to me. Examination with a hand lens convinced me 

 that the rock could not be a concretion of the " blue ground," but was 

 truly holocrystalline and allied to the eclogites. Sir W. Crookes 

 generously waived his own claim to study the specimen, and obtained 

 for me permission from Mr. Tmbenbach to have slices cut from it. I 

 gladly take this opportunity of expressing my gratitude to both gentle- 

 men ; to Sir W. Crookes, for allowing me to carry out this interesting 

 investigation, and to Mr. Tmbenbach for his great liberality in placing at 

 my disposal a considerable suite of specimens (including other boulders) 

 from the Newlands mines, and for the trouble which he has taken in 

 affording me the necessary information. 



* A. W. Stelzner, ' Sitzungsber. u. Abhandl. der Isis ' (Dresden), 1893 (April), 

 p. 71, calls attention to the fact that these show signs of attrition and that they 

 range in size from a few cubic millimetres upwards, being sometimes large boulders. 

 Among the materials (at Kimberley) he mentions both granite and eclogite. 



f For the rock itself he proposed the name " kimberlite." 



X In other words, that the volcano (as occasionally has happened) had ejected 

 little or no lava or scor.a, discharging only steam and hot water, with shattered rock. 

 This view is held by Max Bauer, in ' Edelsteinkunde,' p. 225, which, however, I 

 had not seen when this paper was written. 



