146 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 1, 



i an oz. is the usual limit to the size of " nuggets" even in the 

 richest veins (such as have yielded, on crushing, from 5 to 30 oz. to 

 the ton of quartz), whereas there does not appear to be any limit to 

 the size of the lumps found in the drifts. This is an undoubted fact, 

 and apparently a very strong argument in favour of the upper, now 

 denuded, portions of the "reefs" having been much richer than 

 anything we ever find either on or beneath the present surface. At 

 the same time I must add that I am unable myself to discover, 

 neither have I ever heard, any satisfactory explanation of this 

 peculiar distribution of the precious metal in the quartz-veins. The 

 very frequent intimate mixture of gold, both chemically and mecha- 

 nically, with other metalliferous ores and native metals in the same 

 vein or " quartz-reef," seems to me to preclude the supposition of a 

 force having operated in the distribution of gold entirely different 

 from that which has operated in the distribution of the other metals 

 and metalliferous ores which we now find associated with the gold ; 

 and it seems to me very difficult to believe that the position of the 

 gold, as we now find it, in the solid " quartz -reefs," and sometimes 

 completely enveloped in crystalline quartz, is entirely due to sub- 

 limation ; on this supposition alone, however, I imagine, could the 

 superior richness of the upper portions of the veins be satisfactorily 

 explained. In what state was the quartz when the gold was sub- 

 limed into it ? and how is it that we find no evidence whatever of the 

 action of such an intense and long- continued heat on the slates and 

 sandstones which are in immediate contact with the gold-bearing 

 quartz ? It certainly appears to me that the cause, whatever it may 

 have been, which has operated in the formation and filling of mineral 

 veins generally, whether of tin, lead, copper, silver, antimony, or 

 any other mineral, has also operated in the formation and filling of 

 our gold-quartz-veins, which are, so far as I can make out, whether 

 as regards their mode of occurrence, physical structure, or mineral 

 character, strictly analogous to all other mineral veins. I should be 

 very glad to learn what is now the generally received opinion on the 

 subject of the formation and filling of mineral veins. 



Is it not possible that the large lumps of gold and the general 

 richness of the older drifts might be accounted for, partly, by the 

 enormous amount of natural crushing and washing of the quartz, 

 and consequent concentration of the gold, which must have taken 

 place during the deposit of our gold-drifts, and partly also by some 

 combined chemical and mechanical action operating on the liberated 

 gold in the drifts during the long- continued and violent volcanic 

 eruptions of which we have such ample evidence during the later 

 Pliocene period ? From all I have seen in this country, I certainly 

 think we must look for some other explanation of the occurrence of 

 our big lumps of gold in the drifts, besides the superior richness of 

 the denuded upper surfaces of the veins. Saline waters are very 

 abundant in all our formations, and chlorides are the prevailing salts 

 found in them. 



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