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University of California Publications. [Geology 



paper deals, is but a very limited portion of the Egan Range. 

 It lies in a pass through the range a few miles southwest of the 

 town of Ely. The district comprises a belt varying little from 

 a mile in width and having a length of about six miles. This 

 belt has an east and west trend and thus lies transverse to the 

 general course of the range. The mineralization of the district 

 which gives it its economic importance is intimately and genet- 

 ically connected with an irregular intrusion of "porphyry" cut- 

 ting Carboniferous rocks and occupying the center of the belt. 

 Ore deposits are found both in this porphyry mass and in the 

 sedimentary rocks which border it. In the porphyry itself are 

 found copper ores in large quantity. In the limestones on the 

 northern flank of the porphyry zone, particularly toward its 

 eastern end, are limited bodies of lead ores carrying some silver ; 

 and on the southern flank, also at the eastern end of the belt, 

 occur gold ores in ledges in the sedimentary rocks. The silver 

 lead ores have as yet not been found in sufficiently large bodies 

 to warrant permanent mining operations, although considerable 

 prospecting has been done and some ore has been shipped. The 

 gold ores at the Chainman and Saxton mines have attracted the 

 attention of capital sufficient for the erection of extensive and 

 costly plants for their reduction, but the attempt to win the 

 gold has been apparently unsuccessful and both plants are now* 

 idle. The chief interest in the district now centers in the copper 

 deposits which give much promise of being mined on a large 

 scale in the near future. The chief localities in the district 

 where these ores have been developed by mining operations on 

 a notable scale are at the Ruth Mine in the eastern part of the 

 belt, at Copper Flat in the middle,- and in the vicinity of Pilot 

 Knob at the west end. Besides these, however, there are numer- 

 ous prospects and mining locations throughout the district. 



In the following account of the geology of the district, its 

 limits will be assumed for purposes of description to be coter- 

 minous with those of the geological map which accompanies this 

 paper, f The topographic base of the map upon which the geolog- 

 ical formations are delineated was surveyed and drawn by Mr. 



* 1905. 



t While this paper was passing through the press the map was destroyed 

 in the San Francisco fire. It may be reconstructed and issued later. — Ed. 



