EUBY HILL DEPOSITS. 301 



Ruby Hill Ore Deposits. Mr. J. S. Curtis, in his elaborate monograph upon 

 the ore deposits of Ruby Hill, has embodied the results of much careful 

 investigation of the underground exploitations of the mines. His work is 

 accompanied by numerous vertical and cross sections, compiled from the 

 original mine surveys, indicating the positions of the different ore bodies 

 and their mutual relations. It is unnecessary, therefore, to enter into the 

 details of the economic geology, and only such facts will be given as will 

 enable the reader to form a correct conception of the geological position 

 and mode of occurrence of the ore bodies, not only upon Ruby Hill but 

 those found throughout the district. Ruby Hill, from a geological point of 

 view, may be taken as typical of the deposits in what has been designated 

 as the Prospect Mountain uplift. For the details of the mines, and their 

 extensive underground workings the reader is referred to Mr. Curtis's report. 

 In chapter v, of this report, upon the descriptive geology, there will be 

 found an account of the geological structure of Ruby Hill and Adams 

 Hill. 



By reference to the accompanying map (PL i,) and section (Fig. 3, PL 

 ii,) it will be seen that Ruby Hill is made up of the tliree underlying forma- 

 tions of the Cambrian. They possess a fairly uniform dip, although pre- 

 senting occasional abrupt changes due to faults and fractures. This dip 

 along the surface may be taken at 40, and in the lowest workings of the 

 Richmond mine, which have reached a depth of over 1,200 feet, this angle 

 of inclination is still maintained. At the surface the line of contact between 

 the quartzite and limestone is easily made out all the way from the Jackson 

 fault to the west base of Ruby Hill. Near this latter fault the contact is 

 first observed just west of the American shaft and the Jackson mine. It 

 crosses the summit of the spur on which the Phoenix mine is situated and 

 follows along the southern slope of Ruby Hill, the quartzite at one point 

 rising to within 160 feet of the summit. In the underground workings flu- 

 plane of contact between the quartzite and limestone has been exposed in 

 all the mines and at very many of the levels, the latter frequently running 

 along the contact of the two formations and occasionally cutting the 

 quartzite where it projects to the north beyond the course of the drifts. 

 Numerous cross-cuts have also been run into the underlying rock. 



