188 University of California Publications. [Geology 



The writer had hoped to present even more conclusive evi- 

 dence of successive deposition and its recency, but owing to the 

 fact that the lowest mine workings are not open to outsiders, 

 this became impossible. However, such evidence as already pos- 

 sessed is as follows : 



In the ore bodies opened within the last year on the "sec- 

 ondary vein" now worked, some pertinent facts presented them- 

 selves. The finest specimens of ore show often very perfect crys- 

 tals of stephanite and argentite coating, or wedged between, 

 quartz crystals. Coating one side, the downward side, of all the 

 minerals, is a thin layer of calcareo-siliceous material. Below the 

 surface crystals of ore and quartz is a layer of quartz, resting in 

 turn upon a second layer of calcareo-siliceous matter. This shows 

 below it a second layer of ore, resting upon quartz crystals, and 

 so on, the series often repeating itself several times more or less 

 perfectly. In that portion of the ore occurring in the lower 

 depths, from which the water has been drained but a short time, 

 the surface layers of ore, quai'tz and calcareo-siliceous matter 

 showed clear and fresh, while on standing in the open, or in the 

 higher portions of the vein, the same minerals appeared dusty 

 and old. In some of the vugs in the lower portion of the ore 

 body, quite a number of small but perfect rhombohedra of calcite 

 were found ; also, as noted by Becker, old fractures in the ore, 

 caused by faulting movements, are cemented with quartz and ore. 

 In the ores now worked, however, the motion appears to have 

 been a pulling apart, for brecciation, though present, is rare, and 

 the two sides of a cemented break are usually fully complemen- 

 tary. This process of successive deposition is not limited to the 

 Virginia City portion of the lode, but is found quite well de- 

 veloped in the Gold Hill mines, and in the calcite gangue of the 

 Justice ore body. 



Further uncemented fractures present themselves as indi- 

 cators of motion up to the present time, since the withdrawal of 

 the waters by the mine pumps. The great volume of water still 

 entering the lower workings also contributes abundant proof of 

 fissures kept open by late motion, for the lode proper, where cut 

 by the shaft, is reported to have been completely filled with 

 quartz. 



