32 SILVER-LEAD DEPOSITS OF EUREKA, NEVADA. 



between it and the shale below the fifth level. On the ninth it has been 

 cross-cut for over 100 feet without the shale being encountered. The 

 diagram, Fig. 1, represents the relative positions of the mineral-bearing 

 limestone, fissure, stratified limestone, and shale, as they are developed by 

 a cross-cut. The fissure is not often wide, but it exhibits unmistakable 

 signs of a great upward movement of the country to the southwest of it. 

 In places there are vertical striations, and the hard stratified limestone 

 which forms its hanging wall is often polished as smooth as glass. The 

 strata immediately adjoining the fissure are nearly parallel with it, but as 

 they approach the shale their angle of dip becomes less until it is frequently 

 as small as 20°. The contact of the stratified limestone and shale is very 

 irregular, the strata of the two formations being intermingled, so that there 

 is no well-defined line of demarkation between the two. This contact, as 

 far as can be determined by the examination of the limited portion exposed 

 in a drift, has less dip than the main fissure, but the dip of the bedding- 

 planes of the shale conform very nearly to those of the limestone. The 

 curvature of the planes of bedding in limestone and shale shows the upward 

 motion of the southwest country. The upper portion of the Prospect 

 Mountain limestone which underlay the shale retained its stratification, and 

 is now found to the northeast of the fissure, while the lower portion was 

 forced upward to the southwest of the fissure, its stratification being for the 

 most part obliterated by the crushing accompanying its translocation. This 

 stratified limestone is of dark color, and is similar in character to that com- 

 posing a large block which at the uplifting of the southwest country was 

 left in a comparatively undisturbed condition. This rock can be observed 

 on the sixth level of the Richmond, near the A. C. line (the dividing line 

 between the Richmond and Albion mines), in the widest part of the min- 

 eral belt. 



The places where cross-cuts have been driven up to the shale are not 

 as numerous as could be wished, but there are enough of them to establish 

 the general relative position of the fissure and shale, and it cannot be rea- 

 sonably doubted that the fault is continuous between the points where it 

 has been laid bare. This fissure has very nearly the same dip and strike 

 that it had in the mines to the southeast. It extends through the Richmond 



