G 



papers of Mr. Dunn and Mr. AV. H. Huddleston, with special 

 reference to the theory of the volcanic origin of the "pipes" 

 in which the diamonds occur, iirst advanced by Professor 

 E. Cohen, of Strasburg. 



Tlie strata at Kimberley mine (from which the specimens 

 referred to in this paper were kind^}^ sent by Mr. Loewenthal) 

 are then described; two shafts which have been sunk there 

 — one in the "pipe," the other in the shale near it — passed 

 tlirough the following strata. : — 



(1) ''Pipe." 



Red Sand 3 feet. 



Tufaceous Limestone 15 „ 



Soft yellow earthy dia- 

 mond rock 33 „ 



Soft blue diamond rock 



proved to 282 „ 



Total excavated... 3 30 feet. 



(2) "Outside the Pipe." 



Red Sand 3 feet. 



Tufaceous Limestone 5 ,, 



Yellow Shale 20 „ 



Black carbonaceous do. 10 „ 

 Two thin bands of black 



dust in Shale 1 foot. 



Black Shale 236 feet. 



Dolerite 2 ,, 



I Total excavated ... 2 77 feet. 



The diamonds are found in the yellow and blue "Stuff" 

 along with garnets, mica, bronzite, ilmenite, pyrite, &c., and 

 are separated by washing the broken-up earth in sluices 

 similar to those used in gold mining. The annual value of 

 the diamonds from Kimberley is said to be £3,750,000, and 

 the total amount raised since 1870, to reach tlie enormous 

 sum of £40,000,000. 



The specimens forwarded were as follows : — 



I. A compact greenish-grey rock, labelled " The Hard 

 Rock." 



II. A compact rock of dull rusty-brown colour, labelled 

 " Layer of Ironstone." 



III. A friable earthy rock of greenish-blue colour in 

 which the diamonds occur. 



lY. A mixture of several minerals, in pieces about the 

 size of a pea, labelled "Coarse heavy Deposit, Kimberley 

 blue ground." 



