44 SILVER-LEAD DEPOSITS OF EUREKA, NEVADA. 



160 feet from the shaft. It will be seen that both of these cross-cuts are 

 run through the above-mentioned promontory, and that they give some idea 

 of its shape at the depth at which they were run. These cross-cuts and 

 other workings in the Richmond ground near the compromise line prove 

 that the quartzite in which the shaft is sunk is the main body of quartzite 

 which underlies the limestone of Ruby Hill. (See Plate XIV.) 



The narrow quartzite. — At variable distances, according to the depth attained, 

 northwest of the Richmond shaft, the secondary fissure, as the contact fis- 

 sure between quartzite and limestone has been called, leaves the main body 

 of quartzite and passes off into the limestone. It can be seen on all the 

 levels of the Richmond and Albion mines where the workings have been 

 pushed sufficiently to the south and west, but it is particularly well devel- 

 oped on the second and fourth levels of the former, where its course has 

 been followed by drifts until it disappears in the northwest portion of the 

 Albion ground. The most remarkable feature connected with this fissure is 

 the fact that it is accompanied by quartzite. In the upper levels this 

 quartzite is a very thin band, seldom exceeding 10 feet, and often much 

 less, but in the lower levels it is much wider, reaching a breadth of 80 feet 

 on the Richmond ninth level. Its junction with the main body of the 

 quartzite is not clearly shown on any of the levels, but it is considerably 

 northwest of the shaft in the upper levels, and gradually approaches the 

 shaft, as depth is reached, until on the ninth level it is at about the point 

 shown on the horizontal section No. 6, Plate XIV. The fissure is plainest on 

 the upper side of this narrow belt of quartzite, but a parting is nevertheless 

 distinguishable in many places on the under side. There ai-e several cross- 

 faults and undulations in this quartzite, which were probably produced by 

 the primal upheaval. As the problem of the occurrence of the quartzite in 

 this portion of Ruby Hill is as complicated as that of the shale near the 

 compromise line, a detailed examination of its appearance is necessary to 

 a full comprehension of the phenomena attending the formation of the 

 mineral zone. 



Description of the quartzite in detail. — In the Richmond the quartzite is first encoun- 

 tered on the second level, but it has not been as thoroughly explored on that 

 level as it has been on the fourth, 200 feet below it. It is not certain at 



