125 



ORIGIN AND MODE OF OCCURRENCE OF GOLD- 

 BEARING VEINS AND OF THE ASSOCIATED 

 MINERALS. 



By Jonathan C. B. P. Seavejr, C.E., F.G.S., &c. 



\_Read before the Royal Society of N.S.W., 7 September, 1887.'] 



The origin of metalliferous veins and lodes has given rise to many 

 conjectures and theories from time immemorial, and great have 

 been the differences of opinion held by scientific men of all ages 

 as regards the question. In modern times, however, the large 

 amount of information that has been collected, and is yet in 

 course of collection, bearing on the different modes of occurrence 

 of metals and minerals, their chemical and physical properties, 

 and their geological and geographical positions, has placed certain 

 theories regarding the origin of lodes and veins upon a more solid 

 basis from which to reason, and has at the same time relegated 

 others almost to oblivion. 



In the following notes my remarks will be confined more 

 particularly to auriferous veins and deposits, not that I believe 

 they have peculiarities in their modes of occurrence distinct from 

 all other metalliferous lodes, but because this essay is understood 

 to be one on veins and deposits containing gold in such 

 quantities as to be principally worked or prospected for that 

 metal. I propose, moreover, to confine my description chiefly 

 to the gold deposits of Australasia. I not only believe that 

 most of the peculiar phenomena connected with the occurrence 

 of gold-veins and other auriferous deposits may be better studied 

 in that country than anywhere else, but also because a large 

 amount of authentic information has been collected in Australasia 

 regarding these deposits, and I have, personally, had considerable 

 experience there in this class of mining, and so can speak in 

 most cases with a certain amount of authority as to the actual 

 phenomena connected with the mode of occurrence of gold and 

 the associated minerals. 



It has generally been conceded that by whatever means the 

 veins have been filled, the process of opening the fissures, cavities, 

 or crevices in which they exist has been to some extent independent 

 thereof, and so these two branches of the subject ought to be 

 considered separately, but it must be borne in mind that gold 



