150 ORIGIN AND MODE OF OCCURRENCE OF GOLD-BEARING VEINS. 



in width, and gold has been obtained both in quartz veins, 

 striking approximately north and south ; in thin leaders which 

 traverse the auriferous belts in all directions ; and again in slates, 

 which compose the entire mass of the ore channels in some 

 parts of the ground. The claim, which is working on the widest 

 of these channels, lias saved ,£15,000 worth of gold since 1882, 

 and the last 1,498 tons crushed yielded at the rate of 1-J ounces 

 to the ton. 



In many cases the tufaceous rocks of the Thames (N.Z.) are 

 impregnated with sufficient gold to make it worth while crushing 

 them, and in the Waiotahi Mine especially the rock is frequently 

 crushed for the gold it contains. 



The gold-bearing character of the granite at Omeo, Victoria, 

 has already been referred to. I would mention the fact that the 

 late Rev. W. B. Clarke, F.R.S., was the first to call attention to 

 this mode of occurrence of gold in his work entitled the 

 " Southern Gold-fields." 



Gold has also been found in lodes of antimony and bismuth, 

 and also in veins of calcite ; and it is known to exist in the 

 Hawkesbury sandstones of New South Wales which are 

 comparatively unaltered strata of Triassic age. 



The Origin of Gold-bearing Veins. 



In investigating the origin of gold-bearing veins or the manner 

 in which they are most likely to have been formed, I think the 

 foregoing notes have shewn that they have so much in common 

 with other mineral lodes, as regards their actual physical 

 peculiarities and the manner in which they occur in the rocks, 

 that we may consider them to have been formed under very similar 

 circumstances and are dependent to a great extent upon the same 

 laws of nature for their modes of occurrence. 



In seeking therefore to determine the most probable manner in 

 which gold veins and other mineral lodes have been formed, it 

 will be well first to mention some of the different theories that have 

 been propounded on the subject, and after having briefly referred 

 to the various arguments for and against each of these, to consider 

 which, if any, have the best claim to be accepted as most applicable 

 and best able to account for the various phenomena observed in 

 connection with the occurrence of metalliferous lodes, and more 

 particularly those in which gold is the most prominent metal. The 

 various theories proposed may be classed under the following heads : 



1. Igneous injection. 



2. Sublimation. 



3. Aqueous ascension. 



4. Aqueous solution. 



5. Lateral secretion. 



