172 



commonly associated with arsenopyrite, frequently in 

 lenses or nodules forming large nuggets, and almost invar- 

 iably with galena. Small crystals of gold are sometimes 

 found in rhombic dodecahedra and octahedra, generally 

 distorted, with bevelled edges and finely striated surfaces. 

 Plates and scales are often found in the adjacent slate, 

 but close examination always reveals the presence of 

 minute films or threads of quartz traceable to the parent 

 vein. 



Interbedded Veins. 



As has already been pointed out the auriferous veins 

 are found on domes, although in some few cases, as at the 

 Richardson mine, they are found on the pitching parts 

 of anticlines remote from domes. In such cases, however, 

 conditions favourable for ore deposition have been brought 

 about by a notable change in the angle of pitch, producing 

 virtually a doming of the anticline that is not apparent 

 at the surface. 



The distribution of the veins on any particular dome 

 is intimately related to the rock structure, and complexity 

 is introduced by the unsymmetrical character of the 

 domes. On sharp, closely folded anticlines, where the 

 two limbs form an angle of less than 40 or 50 , the veins 

 are found close to the apex and curve over the anticline 

 forming a succession of superimposed saddles, similar to 

 the "saddle-reefs" of Victoria, Australia. On broad 

 folds, on the other hand, where the angle formed by the 

 two limbs is over 45 , the veins are found at a greater 

 distance from the axis, but generally within the limit 

 of curvature of the strata of the fold beyond which the 

 dip ceases to increase and becomes uniform. If one 

 end of a dome is natter than the other, the veins at 

 that end are further removed from the axis than at the 

 other ; and if veins occur on both limbs of a trans- 

 versely unsymmetrical dome those on the limb with the 

 higher angle of dip will be nearer the axis and more 

 abundant than those on the limb with the lower dip. In 

 many districts, the veins are found on one limb only and 

 then they invariably occur on the limb with the higher 

 dip, which is generally the south dip. 



The interbedded veins have a more or less crescentic 

 outcrop. On the sides of long domes, they form nearly 

 straight lines, but finally curve with the strata around the 



