28 T. S. Hart : The Miner cdogical Characters 



as occur at Ballarat East. The pyrite and arsenopyrite of the 

 country rock and the minerals of the reefs may be regarded in 

 the present state of our knowledge as practically contemporaneous. 

 It must, however, be remembered that the quartz reefs of the one 

 field are in some cases of appreciably different ages, as indicated 

 by their relations to one another and to faults. The order of 

 succession in the cavities must not be given too much weight in 

 determining the general process of growth of the reef. 



The masses of gold on the indicators should also X'eceive 

 separate investigation from the ordinary reef. To whatever 

 extent the indicator gold may be secondary (whether that term 

 is used with reference to the time of its formation or to its being 

 regarded as subordinate to a general theory of vein formation), 

 it cannot be referred to any process of surface weathering, for 

 these ricli patches are associated with easily decomposable 

 minerals, and their characters are continuing unchanged in the 

 deepest levels at Ballarat East. 



The mode of association with other minerals and with the 

 quartz also renders impossible any formation by a process of 

 filtration such as recently suggested by one writer (8). Nor can 

 they be due to obstruction to the motion of solutions in view of 

 the nature of the general resistance to the motion of solutions 

 through the fractures and the rocks themselves, for they are in 

 many cases in places where the movement would be easier than 

 usual. 



Whatever may have been the sources and the general causes of 

 the deposition of the minerals of the reefs, there is strong evidence 

 that the position of the richer gold contents has been determined 

 by the presence of carbonaceous matter, or at least of certain 

 favourable slates, which are frequently carbonaceous. We find 

 the saddle reefs of Bendigo following the course of carbonaceous 

 beds on which there has been slipping (15). The veins of Balla- 

 rat East are often rich in crossing thin carbonaceous beds, and 

 the so-called main reefs of the same field are richest in certain 

 favourable slates. In many localities veins are found along the 

 course of the carbonaceous slates, and richest in their laminated 

 parts. The easiest explanation of the indicator masses seems to 

 be to regard them simply as the extreme case of this more 



