8 Anniversary Address. 



butes a gold-producing agency ; and in one instance the Eelstone 

 porphyry, or Elvanite, was undoubtedly found to be the matrix 

 itself, as its broken up fragments were very remunerative. The 

 gold there is like the black Canoona gold, covered by manganic 

 iron. In this spot there is no slate and no quartz ; the inference 

 is, therefore, sound. Moreover, where, in its extension, this 

 Elvanite did traverse slate, there the deposits of gold were richest. 

 In other localities the gold is carried by quartz. Galena (as I 

 have already stated), copper, and iron pyrites, are metals asso- 

 ciated with the gold. 



The strike of these Silurian slates is from S.E. to N.W. ; their 

 average dip, S. 25 W. The quartz lodes, which sometimes appear 

 as continuations of the el vans, dip W. 13 S. Granite bounds the 

 field, and that also is traversed by quartz and elvans, but the 

 gold does not appear to be continued in such quartz. However 

 there is, probably, a connection of some kind. 



The association of Porphyry with Granite in some of our New 

 South "Wales gold-fields was reported by myself, and it is noto- 

 rious what an amount of gold was obtained at Araluen, where a 

 porphyry dyke or elvan cuts through the granite. 



Mr. Daintree gives ground of hope for a wide extension of the 

 field when the vast area of the slates beyond shall have been 

 searched ; but he regards, what to some may be a new feature — 

 Elvanite as a chief indication. He compares the occurrence of 

 the diorites of Gympie, the serpentine dyke of (Janoona, and the 

 hornblendic and felspathic dykes of Mount Wyatt, as similarly 

 influencingthe production of gold, traversing as some of them, mem- 

 bers of the Silurian formation. He further confirms my previous 

 statements respecting the extension of the Secondary rocks of 

 the Maranoa and Barcoo, pointing out their spread from the 

 Thomson to which I had traced them, 300 miles further up to 

 M'Kinlay's range. This report is the more welcome to me, as I 

 had eight months ago received from the accomplished author a 

 numerous series of photographs and a fine collection of the rocks 

 and minerals of the region described. I have also had from Mr. 

 Holmes, the discoverer, copper and gold from the Leichhardt and 

 from Messrs. Henry and Sheaffe, the ores of the Clon curry, men- 

 tioned in my paper of 1867, and Mr. Daintree states that these 



