RUJiV 1111.1. FAULT. :5()3 



lew degrees west of north, passing just west of tlic .lacksdii sluift. From 

 this point westward it is difficidt to foUow the Ruby Hill fault on the 

 surface, as it lies wholly in limestone nioi'e or less concealed by soil and 

 debris, and the rhvolite which to the southeast of the Jackson fault 

 materially aids in trticing the disj)lacement nowhere comes to the surface 

 after crossing the latter fault. At the time the accompanying map was 

 printed the line of the l\uli\- Hill fault had not Ix-eu followed west of the 

 Jackson mine, but since then ^Ir. Curtis has traced it through the under- 

 groiuid workings of all the mines as tar as the e.xtreme limit of exploration 

 in the All)ion. 



According to the investigations of Mr. Curtis the fault after leaving the 

 Phoenix mine runs in a nearly northwest direction, agreeitig closely with its 

 coiu'se on the east side of the Jac^kson fault. It passes just to tlic north- 

 east of the KK shaft and southwest of the Richmond office. It persistently 

 cuts all formations, qnartzites, limestones, and shales alike, scarcely dcAna- 

 ting from a straight line and a[)parently unintluenced bv the physical 

 conditions of the rock. In like manner the fractures and displacements 

 produced by the earlier orographic changes which elevated the region have 

 exerted but little influence on the course of the Ruby Hill fault. A study 

 of the disturbances and dislocations of the strata point to the conclusion 

 that this fault, with its accompanying fissure, was the last dynamic move- 

 ment in the liistorv of Kubv Hill. Wherever underground explorations 

 admitted of observation the average dip of the ii.ssure plane was found to 

 be about 70° to the northeast. Southeast of the Jackson fault the width of 

 the fissure and the dij) of its ])lane are ind<;nown. 



Subsequent to the formation of the tissuri' ami probabh^ nearly coinci- 

 dent with it was the filling of the wider portions with intrusions of rhyolite, 

 notwithstanding the fact that the\' nowheiv (piite reach the siu*face on 

 Ruby Hill. 



Evidence goes to show that the volcanic energy displayed along the 

 fault Vuw expended the greatest activity near its junction with the great 

 Hoo.sac fault, the powerful extravasations of rhyolite gradually dying out 

 toward the northwest, and beyon<l the intersection with the Jackson fault 

 failed to oxcrflow the top of the lissure walls. 'Tlic rlnolites exposed in 



