78 SILVER-LEAD DEPOSITS OF EUREKA, NEVADA. 



of ore bodies which are found at the contact of quartzite and limestone-in 

 the Eureka ground. 



Description of west ore body. — The west ore bod) T , as the second system of 

 chambers in the Richmond mine is called, begins near the surface in the 

 Eureka ground in the neighborhood of the "compromise line." These 

 chambers are all connected with one another in some manner, and most of 

 them are connected with a system of fissures. It pitches north, and as 

 depth is obtained passes through the Richmond and enters the Albion 

 ground. It lies under and northwest of the east ore body, and does not in 

 any place connect with it or directly with the Potts chamber. Neverthe- 

 less, as the upper part of the west ore body lies on or near the quartzite in 

 the Eureka mine, and as in this mine ore is traceable along the quartzite 

 to the Potts chamber, the two ore bodies are indirectly connected. The 

 positions of these ore chutes can be seen in the vertical cross-sections, 

 Plates IX. to XII , and in the elevation, Plate III. From them has been 

 taken very nearly one-half of the ore extracted from Ruby Hill. 



Connection of ore bodies with depressions in the quartzite. As has beeil Stated ill Chapter 



IV., many of the ore bodies in the Ruby Hill mines are intimately con- 

 nected with sags or depressions in the quartzite; and the manner of forma- 

 tion of these basins was there described. That large ore bodies should be 

 of frequent occurrence in these depressions is not strange when it is remem- 

 bered that the limestone in them was in a shattered and crushed condition, 

 and that the quartzite, with its casing of clay, served to a certain extent 

 to confine the metal-bearing solutions to this limestone mass, where large 

 quantities of those solutions were probably allowed to settle quietly and 

 deposit ore. It was in these basins that the conditions most favorable to 

 ore deposition were found. 



In the Richmond ground, although such depressions in the quartzite 

 occurred in the upper as well as in the lower levels of the mine, they do 

 not seem to have been accompanied by ore bodies, in spite of the fact that 

 the character of the limestone was favorable to ore deposition. This can 

 be accounted for by several facts. The two main ore channels in the Rich- 

 mond mine, the east and west ore bodies, did not approach the quartzite, 

 owing to the fact that the fissures with which they were connected did not 



