Notes on the Area of Intrusive Rocks at Dargo. 145 



This difference in composition in gold from the two classes 

 of areas can be seen in two assays which I now give, in 

 addition to the former, for the purpose of illustration. A is 

 alluvial gold from the Silurian formation at Crooked River, 

 and B alluvial gold from the metamorphic area of Dargo. 



A B 



Au 96-923 ... 82-969 



Ag 2-564 ... 16055 



Oxydisable ) ,,^^ .^.^ 



Metals and loss j ^^^ ^•- ^^^ 



99-979 99-941 



The connection which I have here noted between the 

 geological formation and the amount of alloy with the gold 

 seems not to be confined to the districts I have referred to. 



An examination of the reports of mining surveyors shows 

 reason for suspecting that there is a similar connection 

 between the geological formation and the composition of the 

 gold found in it throughout Victoria.* But it is not so 

 clearly to be made out, because the highest and lowest price 

 paid for gold in any locality is not always necessarily for 

 gold raised there, but also includes gold brought from other 

 places. 



The subject is an interesting one, and capable of throwing 

 light upon the source of the gold, and also upon the processes 

 which have been at work in depositing it in the quartz reefs. 

 But it would require much labour to work it out in a 

 satisfactory manner. Examinations would have to be made 

 both of reef and alluvial gold from the same locality, and of 

 reef gold from different parts and depths in the same mine. 

 This should be repeated in many places and in different 

 formations. In connection with such a series of examina- 

 tions there should be also another of the local rocks, and 

 also of rocks taken from different depths and places in the 

 several mines from which the gold had been collected for 

 examination. 



The comparison of such gold assays, and of the micro- 

 scopical and chemical examinations of the rocks, would, in 

 all probability, lead to some conclusions as to whether the 



* Eeports of the Mining Surveyors. Published by the Department of 

 Mines. " Table showing the lowest and highest prices paid for gold." Years 

 1880 to 1885. 



