0. A. Derby — Gold-bearing Lode of Passagern. 189 



The specimen represented in fig. 3 exhibits some other phases 

 of the mineralization process. The fissures of the fractured 

 quartz-feldspar rock are here of considerable width and the 

 filling is exclusively of tourmaline with only here and there a 

 small isolated crystal of pyrite, of which not more than a 

 dozen can be counted on the considerable surface here shown. 

 The feldspar is completely sericitized and it is thus clear that 

 this effect was produced by the agent that introduced the 

 tourmaline rather than the one that brought in the metallic 

 sulphides. It is also evident that two distinct agents were 

 involved and that, in places at least, these acted quite independ- 

 ently one from the other. In the lower part of this specimen 



Fig. 4. 



the tourmaline has a small admixture of granular quartz giv- 

 ing a friable tourmalinfels with a slight development of a 

 schistose structure. Elsewhere on this and the other speci- 

 mens figured, the vein quartz is impregnated with tourmaline, 

 giving, as Hnssak has already remarked, a massive rock resem- 

 bling the luxullianite of Cornwall. 



The block of ore represented in fig. 4 shows a mass of dis- 

 tinctly schistose tourmalin/els charged with arsenopyrite (white 

 in the figure) which clearly fills fractures along planes of 

 schistosity, and across the intervening plates of rock. This 

 case completes the evidence, suggested by figs. 2 and 3, of the 

 independence of the tourmalinization and the sulphuritization 

 of the original vein rock, and shows that the former process 

 preceded the latter. Other specimens showing larger fissures 

 filled with a somewhat spongy mass of a granular arsenopyrite 

 have scattered needles of tourmaline with every appearance of 

 having been formed in situ, so that it is tolerably certain 



