456 Norman Taylor — The Gudgegong Diamond Field. • 



the Gwydir Eiver, New England District, New South Wales) tin and 

 diamond mines were reported on by my late colleague, Mr. C. S. 

 Wilkinson (Mines, etc., New South Wales, 1875, p. 79); and at Bald 

 Hill, near Hill End, Lambaroora, diamonds were also reported on 

 by Prof. Liversidge (Mines, etc., New South Wales, 1875, p. 115), 

 where some tolerably large ones were found — one slightly over 

 three carats (9-6 grains Troy), and another one and a half carats 

 (4 - 5 grains Troy). The late Professor Thomson was shown some 

 diamonds which were said to have been obtained in the sands at 

 the mouth of the Clarence Eiver ; and the writer was shown one 

 from a drift underlying basalt near Trunkey Creek, Tuena, Aber- 

 crombie Eiver. In all these instances, with the exception of Borah 

 Creek, the surrounding country is entirely Palaeozoic, intersected, 

 however, by dykes and masses of various igneous rocks. 



The fact of the diamonds exhibiting structural or growth planes 

 is, I think, sufficient to enable us to disregard the igneous rocks for 

 their origin, unless some of these rocks (the granites and green- 

 stones) are metamorphic. Wohler asserted that the diamond could 

 not have been formed at a high temperature, least of all by fusion. 

 Brewster thought that the old conjecture, that diamonds were of 

 vegetable origin, was confirmed by their optical properties, and 

 analogy to amber. 



The occurrence of tin with the diamond at Borah Creek, New South 

 Wales, and at Beechworth, Victoria, both in granitic areas, indicates 

 granite as their possible source ; but tin always occurs with diamond, 

 in small quantity, in the other districts mentioned, which are more 

 numerous, and all in older sedimentary rock areas. 



In Mines and Mineral Statistics of New South Wales, 1875, p. 79, 

 Mr. Wilkinson states that the Borah Creek tin and diamonds occur 

 in a newer drift, a wash from the older Miocene drift underlying 

 the basalt, and that the entire watershed of the country is granitic. 

 He also notices the occurrence of small black pebbles of jasper, 

 which seem to him to indicate that the rock producing the diamond 

 may have been entirely denuded away. On this field the diamonds 

 average in weight about one carat grain each (the largest 5 -5 carat 

 grains), and their facets and edges are never waterworn or abraded. 

 On page 88, speaking of diamonds and tin, Mr. Wilkinson states, 

 "There seems but little doubt that they have been derived from the 

 older Tertiary gravels ; and this is an agreement with the observa- 

 tions of the late Professor Thomson and Mr. Norman Taylor on the 

 Cudgegong diamond field." Mr. Wilkinson seems partly to have 

 subscribed to the writer's view that the older drift is the matrix of 

 the diamond. 



In Captain Burton's " Highlands of Brazil," vol. ii. page 137, he 

 says, " For reasons that will presently appear, it (the diamond) is 

 evidently younger at times than the formation of gold, and it is 

 probably still forming, and with capacity for growth." The writer 

 failed, however, to notice the reasons that were to appear. 



Professor Liversidge remarks that the Bingera diamond field is 

 surrounded by rocks of Devonian or Carboniferous age, but that he 



