KUBY HILL AND PINTO FAULTS. 17 



the north. No precise measurement of the amount of displacement along 

 the east base of Prospect Ridge can be given, but estimating it from the 

 known thickness of the strata lying between the summit of the Eureka 

 quartzite and the base of the Lower Coal-measures as given in the Eureka 

 section, we have a vertical movement of 12,800 feet. Now, if we suppose, 

 and it seems highly probable, that there are 300 or 400 feet of limestones 

 beneath the beds exposed at the surface, and that the upper portion of 

 the Eureka quartzite is also wanting, we have a displacement of over 13,000 

 feet. Probably the vertical movement at its maximum displacement 

 amounted to more than 2J miles, lying wholly within Paleozoic rocks. 



Ruby Hill Fault. The branch fault which leaves the main one just after 

 it enters New York Canyon from the south trends northwesterly across the 

 slope of Prospect Ridge, thence across Ruby Hill, probably connecting 

 with the Spring Valley fault although it has never been traced beyond the 

 Richmond and Albion mines. It has been designated the Ruby Hill fault. 

 On the atlas sheet its course is indicated only a short distance beyond the 

 Jackson fault, its true position on Ruby Hill not having been accurately 

 located until after the printing of the map. Although the Ruby Hill fault 

 possesses features of great economic importance bearing upon the ore de- 

 posits of the district, it is by no means so profound a displacement as the 

 Hoosac and is measured by hundreds instead of thousands of feet. The 

 dynamic movements which produced it have not influenced in any marked 

 manner the structural features of the country, presenting, in this respect, 

 the greatest possible contrast with the main Hoosac fault. There is some 

 reason for the opinion that the Ruby Hill fault is of later date than the main 

 fault, and belongs to the period of Tertiary eruptions. A more detailed 

 description of this fault will be found in the chapter devoted to the discus- 

 sions of the ore deposits. 



Pinto Fault. This fault is situated about 2 miles to the east and nearly 

 parallel with the Hoosac fault, which it closely resembles in structural 

 features. Like the Hoosac, its course can not be traced with precision, yet 

 the geological characters are so distinctive that there exist scarcely any 

 difficulties in the way of determining its main trend across the mountains 

 as it sharply defines the boundary between the elevated County Peak and 

 MON xx 2 



