142 Notes on the Area of Intrusive Rocks at Dargo. 



three of the latter. The remaining molecular proportions 

 should then give the amphibole, with a small remainder of 

 silica representing the free quartz. In this calculation the 

 small amount of Fe^Og is regarded as indicating the magne- 

 tite, and the minute amount of talc is disregarded. The 

 xatio between the remaining components which are thus 

 assigned to amphibole are such as to fall within the limits 

 given by Rammelsberg for an aluminous hornblende, being 



II II 



AI2 to K as 1' to 3', and R to Si as 1*5 to 1** Taken in 

 percentages, the rock may accordingly be composed as 

 follows : — 



Magnetite ... 



2-34 



Kaolin 



5-69 



Chlorite ... 



9-72 



Andesine ... 



... 86-55 



Hornblende 



... 83-55 



Quartz 



... 12-15 



10000 

 AuEiFERous Veins in the Dargo Area. 



Gold-mining has been carried on for many years in 

 various parts of the intrusive areas referred to in these 

 notes. Alluvial gold in payable amount has been found at 

 Dargo, Tucker Creek, Granite Creek, and other places, 

 and in less amount is almost everywhere to be met with 

 in the gravel of the streams. The alluvial gold is either 

 in small laminated flakes or in ragged pieces, according as it 

 is found in the larger streams, or in localities near to the 

 veins from which it has been set free. In a number of 

 places small gold-bearing quartz veins have been discovered, 

 and at Tucker Creek, Budgee Budgee, and Orr's Creek such 

 have been more or less worked. 



At Orr's Creek, to which place these notes especially 

 refer, a number of small quartz veins have been worked for 

 several years back in the hornfels rocks immediately adjoin- 

 ing the contact with quartz diorites. This mine is called 

 the " Exhibition," and I now give some particulars concern- 

 ing it, which are of interest, as showing the character of 

 the small quartz lodes and veins,, the wearing down of 

 which has set free the alluvial gold of the district. 



* Mineralchemie, page 418. 



