PROSPECT MOUNTAIN QUARTZITE. 35 



Prospect Mountain Quartzite. This group lies at the base of the Cambrian 

 series at Eureka and is consequently the oldest sedimentary rock exposed. 

 It takes its name from the peak, the highest point along the ridge, where it 

 reaches its broadest development and forms the greater part of its western 

 slope. With one or two breaks in the continuity, the quartzite may be 

 traced along the base of the ridge northward to Ruby Hill, where, as the 

 footwall of the Richmond and Eureka Consolidated Mines, it becomes 

 of considerable economic interest. There can be no question that the 

 quartzite of Prospect Peak and that of Ruby Hill are identical. From 

 Ruby Hill the quartzite curves around the end of the mountain, following 

 the east side of the ridge, and stretches southward for more than a mile 

 until abruptly lost by a fault. The only occurrence in the district of this 

 quartzite is on Prospect Ridge. On Prospect Peak the strata have a thick- 

 ness of 1,500 feet and occur distinctly bedded, but in some localities all 

 lines of stratification appear to be wanting. At the base of the series the 

 beds are largely composed of conglomerates and brecciated masses firmly 

 cemented together with ferruginous material, with the weathered surfaces 

 deeply stained by iron. In the conglomerates quartz pebbles may occasion- 

 ally be seen, showing compression and flattening on their broader sides, 

 arranged in beds parallel to the planes of stratification. The upper beds 

 are usually finer grained, carrying less iron oxide. In the Charter Tunnel, 

 the only locality where they have been exposed by mining exploration, 

 they show highly metamorphosed beds derived from impure siliceous mate- 

 rial. 



Interstratified throughout the quartzite are occasional bands of fine 

 grained arenaceous and micaceous shales only a few feet in thickness. No 

 organic remains have been found in this group, although diligent search 

 was made in the interstratified shales, as, if they occur, they would be of 

 the highest paleontological interest, extending the Cambrian fauna lower 

 than has yet been known in the Great Basin. The Prospect Mountain 

 quartzite differs from the Eureka quartzite, the next overlying siliceous 

 group, in being more ferruginous and in general less uniform in texture, 

 carrying throughout more or less clayey material, while the latter quartzite 

 is a nearly pure, highly altered sandstone. 



