GEOLOGY OF RUBY HILL. H5 



can be made of the thickness. There are, however, only 200 or 300 feet 

 of beds before the horizon is sharply cut on" bv the Hoosac fault bringing 

 in the Carboniferous in juxtaposition with it. 



Caribou Hill, separated from McCoy's Ridge by Purple Mountain, stands 

 out as a prominent topographical feature. It is capped by the same 

 Eureka quartzite. There are only 200 feet of beds and consequently the 

 Lone Mountain limestones are wholly wanting. It is this cap of quamite 

 which has protected from erosion the underlying limestones. Here, again, 

 in a narrow ravine at the west base of the hill, in the underlying limestone 

 immediately beneath the quartzite, the Receptaculites beds occur, with several 

 characteristic species, offering additional proof, if any was needed, as to their 

 geological position. From Caribou Hill northward no outcrops of the 

 Eureka quartzite were recognized. The Pogonip limestones present low, 

 flat-topped ridges inclined northward, gradually passing beneath the recent 

 deposits of Diamond Valley. 



RUBY HILL REGIOX. 



Ruby Hill and Adams Hill together occupy a small but clearly denned 

 area which may be considered simply the northern extension of Prospect 

 Ridge. The Jackson fault sharply outlines this area on the east side, while 

 the recent accumulations along the line of the Spring Valley fault limit it on 

 the west side. The geological importance of the region is mainly derived 

 from the enormous ore deposits found in the limestones of Ruby Hill, which 

 had yielded, up to the time of this investigation, over 860,000,000 in 

 precious metals. In general the orographic structure is simple, and only in 

 detail in the immediate neighborhood of Ruby Hill is it in anv way complex. 



On Plate i will be found a geological map of Ruby Hill and the adja- 

 cent country, prepared from the large atlas sheets for more easy reference 

 to the text. Unfortunately the line between atlas sheets vn and viu runs 

 directly across this area, interfering greatly with the clear understanding 

 of the structural relations of the beds of Prospect Ridge with those of 

 the Ruby Hill as well as with those lying east of the .Jackson fault. Hy 

 referring to the map it will be readily seen that the Jackson fault cuts off 

 the Cambrian strata and brings the Pogonip up against the entire series. 



