504 



THE ORE-DEPOSITS OF BORAH CREEK, 



A noticeable feature of the lode is that there is practically no 

 zone of oxidation, the sulphides being found right at the surface. 

 What little oxidised ore does exist, occurs on the slope of the hill 

 near Moore's and Davis' shafts, and extends only to a depth of 

 30 feet. A very interesting example of metasomatic replace- 

 ment of galena by quartz is to be seen in one of the upper stopes. 

 Here the crystallised galena can be traced gradually into pure 

 quartz. The quartz has retained the cleavages of galena to per- 

 fection. Samples of the latter, in thin seams between flat sheets 



Scale 



2 Feet 



Text-fig. 4. — Section of King Conrad Lode, iUustrating sequence 

 of the ore-deposition, 



a, granite slightly altered next the lode — b, arseuopyrite — c, 

 sphalerite and chalcopyrite — d, quartz intergrown with argen- 

 tiferous galena and sphalerite — e, argentiferous galena — c^ small 

 banded veins, chiefly sphalerite and galena. 



The Conrad Lode. 



of quartz, may be observed where the replacement is not quite 

 complete. The replacement has been effected by surface-waters. 

 It is worthy of note that this metasomatic action has taken 

 place in the main ore-shoot of the King Conrad Lode. A glance 

 at text-fig. 2 shows the position (marked A) with reference to the 

 ore-shoot, which may be seen as an irregularly shaped mass 

 pitching easterly. 



The Conrad Lode is undoubtedly the main ore-body; it per- 

 sists for considerably more than a mile in length, and has been 



