BY L. A. COTTON. 837 



stream side of it. A similar dyke, or small neck, of an almost 

 identical rock was found at Staggy Creek, some 4 miles north- 

 west of this occurrence. In this case, also, diamonds were found 

 in the gravels overlying the dolerite-mass. The occurrence of 

 two such masses of dolerite, associated with the diamond in this 

 area, gives strong grounds for supposing that the whole of the 

 diamonds of the Copeton field have been derived from similar 

 sources. The two known dolerite-masses are so situated that 

 they cannot have supplied more than a portion of the Tertiary 

 deposits. 



It is probable that most of the sources of supply of the 

 diamonds are now concealed by the later basalt-tiows, in the same 

 way as the Oakey Creek occurrence. 



In conclusion, I take the opportunity of here thanking those 

 who have assisted me in this work. To the miners of Copeton, 

 and pre-eminently to Mr. A. R. Pike, my best thanks are due 

 for kind assistance in field-work. I am also indebted to Pro- 

 fessor David, for help and encouragement during the preparation 

 of this paper; and to Mr. A. Pain, for some assistance in rock- 

 analysis. 



BIBLIOGRAPHY. 



1. Andrews, E, C— *'The Geology of the New England Plateau, with 



especial Reference to the Granites of Northern New England." 

 Records Geol. Surv. N. S. Wales, 1905, Vol. viii. 



2. Anderson, W.— Annual Report of the Department of Mines of N. S. 



Wales, 1887. 



3. Cotton, Leo A.— "The Ore-Deposits of Borali Creek." Froc. Linn. 



Soc. N. S. Wales, 1910, Part ii. 



4. David, T. W. E. D.— Sydney Morning Herald, 19th and 26th January, 



1907. 

 4a. Mining Journal, 27th August, 1907. 



5. Hartog, Victor. — " Petrographic Note on the Diamond-bearing Peri- 



dotite of Kimberley, South Africa." Economic Geology, Vol. iv., 

 No.5. 



6. Pike, A. R. — Australian Mining Standard, 27th January and 3rd 



February, 1909. 



6a. Inverell Argus, 31st March, 1911. 



