804 DIAMOND-DEPOSITS OF COt'ETON, N.S.W., 



time to time by officers of the Department of Mines, the chief of 

 these being that of W. Anderson(2) in 1887. This communica- 

 tion was accompanied by a geological map of the district in the 

 neighbourhood of Copeton. This map, somewhat modified and 

 added to, has been incorporated in this paper. Another report 

 of some value is that by G. A. Stonier(8) in 1894. An excellent 

 summary of the work accomplished, up to the date of publication, 

 was given by Mr. Pittman(7) in his book, " The Mineral Re- 

 sources of New South Wales," which appeared in 1901. The 

 most interesting fact, from the scientific standpoint, was the dis- 

 covery of a diamond in its true matrix by Messrs, Pike and 

 O'Donnel in 1904. An account of tliis was published in the 

 Annual Report of the Department of Mines for that year. 



More recent contributions to the literature of the subject have 

 been made by Professor David(4), Mr. J. A. ThompsonO), and 

 Mr. A. R. Pike(6). 



ii. The Naturk of the Leads. 



The diamond-bearing drifts fringe the depression which lies 

 between Cope's Creek and the Gwydir River. (See Plate xci.,fig. 2). 

 As the first diamonds discovered were won from recent alluvials^ 

 these will be first described. 



Reference has already been made to the fact that diamonds 

 were first found by miners in search of alluvial tin. In all these 

 cases, these gems had been redistributed from Tertiary river- 

 gravels. By this process, small quantities of these gravels were 

 added to relatively large masses of recent river-gravels. In con- 

 sequence of this, it is at once apparent that the diamonds must 

 be scattered through a much greater amount of barren river- 

 gravel than was the case in the old leads. In exceptional cases, 

 where the denudation of the Tertiary gravels was rapidly eff'ected, 

 the recent alluvial deposits have proved payable. Koh-i-noor 

 deposit and the old football-ground at Copeton are examples of 

 this type of occurrence. The former place lies between two well 

 defined portions of the Tertiary lead. The diamonds are here 

 found distributed through a mass of basalt-boulders, which have 

 been worn down from the neighbouring hills. These boulders 



