34 SILVER-LEAD DEPOSITS OF EUREKA, NEVADA. 



quartzite moving upward along the Ruby Hill fault. It is very likely that 

 this distance will be considerably less, though there is not much probability 

 that the fault will enter the limestone within 1,500 feet below the Eureka 

 twelfth level. These calculations are made for the portion of country from 

 which the ideal section, Plate IV., has been made. 



secondary fissure. — At the time of the disturbance which produced the main 

 fault another and secondary fissure was formed along the contact of the 

 quartzite and limestone, and the quartzite was raised higher than the lime- 

 stone, giving rise to the formation of a limestone wedge between the quartz- 

 ite on the one hand and the main fissure on the other. The dip of the 

 quartzite contact does not greatly exceed 40°, while the dip of the main 

 fissure is about 70°. The two surfaces of motion therefore approach each 

 other and must eventually meet. In some mines this has already been 

 shown to be the case, and the line of junction is exposed at various depths 

 in the lower workings of those southeast of the compromise line. To the 

 northwest of this line the lowest workings have not reached the junction. 



The crushed condition of the limestone wedge is due to the upward 

 movement of the southwestern country against the hanging wall of the main 

 fissure. This upward movement also accounts in some measure for the dis- 

 turbed nature of the contact between the quartzite and limestone, though 

 there is no doubt but that there were many irregularities in this contact 

 before the faulting took place. This is shown by the contact between shale 

 and limestone, which is also very irregular, but it could not have been pro- 

 duced by the fault, as it lies in an undisturbed region. The undulations 

 and protuberances in both quartzite and limestone were probably in the 

 main produced by the primary folding which formed the hill 



Up to the present time all the ore of any importance taken from Ruby 

 Hill has been extracted from the country southwest of the Ruby Hill fault, 

 between it and the quartzite. The limestone northeast of the fissure, or the 

 "front limestone," as it has been called, although it has been considerably 

 prospected, has yielded no remuneration. An examination of the vertical 

 cross-sections of the Ruby Hill mines (Plates V. to XII.) will explain the 

 relative positions of the two fissures and of the limestone and ore between 

 them, and the elevation (Plate III.) exhibits the line of their junction. In 



