146 OBIGIN AND MODE OF OCCURRENCE OF GOLD-BEARING VEINS. 



worked, it has an underlay to the northward of about 30° from 

 the horizontal, the strata dipping about 45° in the same direction. 

 It carried most of its gold in the upper levels in a decomposed 

 iron ore or gossan and in a ferruginous quartz of a very hard 

 character. In the lower levels it ran into a solid highly pyritous 

 ore. Other reefs in the same locality seem to be of a similar 

 nature, while some of them contained a very large amount of 

 galena and copper. 



The thickness of the Alma lode was from about eighteen inches 

 to four feet in the underlay shaft at the principal mine, but in 

 other parts of its course it sometimes became even thinner than 

 above, while in others it was over four feet thick ; its underlay 

 also decreased as it went easterly, the dip of the vein becoming 

 greater from the horizontal. I have not, however, visited it for 

 years, but I believe it is being worked at the present time. 



At the Ulooloo old alluvial diggings some nice alluvial gold 

 was obtained. Large iron-stone reefs occur, and one of the leads 

 was richest where a lode of this sort crossed it. The formation 

 of the strata at this place is very peculiar. 



Of gold veins in other parts of the world, those of the United 

 States hold the greatest prominence, and the "Comstock Lode" 

 is certainly the most remarkable auriferous one in that country, 

 and one of the most remarkable in the world. It is situated in 

 the State of Nevada, and occurs upon the side of a diorite hill 

 named Mount Davidson. It occupies for part of its course a 

 line of contact between diorite and diabase rocks, but further 

 north is contained wholly in diabase, and to the south it just 

 touches metamorphic rock on one side while being bounded on 

 the other by diabase. It has been traced for a distance of over 

 four miles in a nearly due N. and S. direction, and it dips towards 

 the East at an angle of about 45° and has a general thickness of from 

 20 to 60 feet. The tissure upon which it has formed is a line of 

 fault. Its vein matter consists of country rock, clay, and quartz, 

 all of which have been much crushed, probably due to the moving 

 of the walls of the tissure on each other. A great heat commenced 

 to prevail in the lower levels of the workings on this lode, which 

 were over 3,000 feet in depth, and I understand that this has so 

 much increased of late that the miners are unable to work for 

 any length of time. 



This lode has yielded enormous returns, over $300,000,000 

 worth of bullion having been taken from it up to 1st June, 1880, 

 and of this $175,000,000 was silver and the remainder gold ; 

 $115,871,000 of this had been paid in dividends. 



Some very interesting investigations connected with metalliferous 

 lodes have been made at these mines, to some of which I shall 

 refer further on in my dissertation on the origin of quartz veins 

 and other auriferous lodes. 



