179 



Angular s. 



Many of the main veins have branches passing into the 

 foot or hanging wall. These branches are termed angulars, 

 and they play an important part in the ore deposition in 

 certain veins. The point from which an angular passes 

 from the main vein into the hanging wall is usually higher 

 than that from which it passes into the footwall, and the 

 intervening portion of the vein is frequently thicker and 

 richer than other portions. Their distribution and atti- 

 tude is dependent on the structure of the dome. In some 

 parts of a dome they may be numerous or completely 

 absent; they may have a general strike and dip quite dif- 

 ferent from what is found in another part of the dome. In 

 crossing the bedding, they generally run nearly perpend- 

 dicularly to the quartzite but obliquely through the slate. 

 In a closely folded anticline they are more numerous at 

 or near the apex, where they often form a reticulated 

 system of veins extending along the axial plane from one 

 lode to an overlying or underlying one. 



The quartz of the angulars differ from that of the main 

 veins in being of a fine, granular texture, free from lamin- 

 ations. 



ORE DISTRIBUTION. 



All the veins are not auriferous. The coarsely crystal- 

 line quartz seldom carries gold, while the laminated veins 

 of oily quartz-bearing sulphides, generally do. In a few 

 auriferous veins the gold seems to have had a fairly uni- 

 form distribution, but experience has shown that in 

 most of them there was more or less segregation into 

 pockets and shoots. 



Some of the richest ore mined has been found in pockets. 

 In the Blackie lead at Oldham the gold was found aggre- 

 gated chiefly in nodules of arsenopyrite ; and in the Hay 

 lead lying 1,800 feet (548 m.) north of the anticline of 

 the same district, an isolated pocket carrying 60 ounces 

 of gold was found at the intersection of an angular with 

 the main lead. 



The great proportion of the ore, however, lies in shoots 

 having more or less definite boundaries and directions. 

 They vary from 20 to 60 feet (6 to 18 m.) or more in 

 breadth and are frequently accompanied by a thickening 

 of the vein. In interstratified veins, many shoots have 

 35063—12^ 



