260 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



Porphyry overlying the Bkie Limestone. The Cohimbia shaft, between 

 the forks of Little Evans, penetrates 30 feet of Gray Porphyr}' and 100 feet 

 of Blue Limestone to the Parting Quartzite beneath. The Humboldt and 

 other shafts between the last mentioned and the Uncle Sam are all in Gray 

 Porphyr}-. At the Uncle Sam shaft the White Porphyry comes to the 

 surface in the crest of the anticlinal fold, whose axis here rises so that for a 

 short distance the porphyry has been eroded off it. The Uncle Sam shaft 

 has been sunk for a depth of 420 feet, passing through 100 feet of White 

 Porphyrv, the underlying Blue Limestone, Parting Quartzite, and White 

 Limestone, and extends 40 feet into the Lower Quartzite, while the Uncle 

 Sam tunnel has been run 250 feet into the overlying Gray Porphyry, and 

 the Powhattan (Q-7) shaft adjoining was sunk through White Porphyry 

 into the Blue Limestone. The Powhattan (Q-9), Rome (Q-6), Eaton 

 (Q-10), and others on the hill above are in Gray Porphyry. 



Yankee Hill anticline. — Of the anticHual ridge Connecting the Little Evans 

 with the Yankee Hill anticline, few data have been obtained. The Little 

 Hoosier, Abe Lincoln, and shafts P-29 and P-38 have penetrated the 

 Wash to the underlying Gray Porphyry, in which the first named has been 

 sunk 170 feet, the moraine material at this point being 120 feet deep. The 

 shaft P-39 has reached the Blue Limestone beneath the Wash, and the 

 Chicago Boy (P-67) passes through the Parting Quartzite into the lower 

 sheet of AVhite Porphyry. This lower sheet of White Porphyry has not 

 been found north of this point, and is supposed to wedge out. 



Little Stray Horse synciine. — In the northern Continuation of the Little Stray 

 Horse synciine the Buffalo shaft and drill-hole, on the Evans moraine ridge, 

 is said to have reached a depth of 450 feet and is still in Gray Porphyry; 

 and the shaft S-10 is also in Gra}^ Porphyry. No other data could be 

 obtained as to the deptli of this basin, so that it can only be said that in its 

 center the contact is probably 500 feet deep at least. 



Big Evans anticline. — Of tlic Big Evans anticliuc, whicli is a continuation 

 to the northward of that shown on the west edge of Fryer Hill, data are 

 still more meager. The Argo (R-5) shaft finds White Porphyry beneath 

 the Wash and is sunk into the underlying Blue Limestone. Adjoining this 

 on the east is the Douglas (R-4«) shaft, and on the north the R-4 shaft. 



