500 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



hydrated ; also, in the fact that it occurs high up on the hill and free from 

 the ordinary covering of Wash, which, no doubt, promotes decomposition 

 and the chemical combination of water in rocks that underlie it. From the 

 staining of rocks eastward, along the outcrop of the contact, and from data 

 obtained from shafts sunk higher up on the hill, it appears that an iron body 

 extends, though not continuously, for some distance to the eastward 



SYNCLINE EAST OF YANKEE HILL. 



The geological structure of the area between Yankee Hill and Weston 

 fault has been already explained in Part I, Chapter V, and is graphically 

 shown in Sections C, D, and L. As yet no considerable ore bodies have 

 been found at the ore horizon in this area; but it seems not to have received 

 the attention it deserves, in view of the good indications afforded by the 

 explorations already made. These may be briefly enumerated as follows: 



The amount of vein material proved on its western rim has been men- 

 tioned above. On the south side, the Little Prince (K-32) shaft passed 

 through 150 feet of Gray Porphyry and 80 feet of White Porphyry to the Blue 

 Limestone horizon, which is here about one hundred and twenty feet thick 

 and entirely replaced by' a porous silicious material, not unlike the granular 

 quartz gangue of the Morning Star mine. At first glance it somewhat 

 resembles a decomposed porphyry, and in it small irregular bodies of sand 

 carbonate, but no limestone, have been found. The Parting Quartzite was 

 found below it. On the lower slopes of the hill the Nora (K-23), Bosco 

 (K-28), Across the Ocean (K-31), and Great Hope (K-30) shafts were 

 sunk through Gray Porphyry to the ore horizon, the first two without find- 

 ing any intervening White Porphyry. In all more or less vein material was 

 found replacing the limestone. The Onota, from which the typical Gray 

 Porphyry was taken for analysis, also reached limestone near the middle of 

 the basin. In the Great Hope quartzite was reached after passing through 

 60 feet of vein material. In the iron vein material some large layers of 

 lime-sand were found, and at 105 feet from the surface a streak of galena 

 five to six feet thick is said to have been passed through, but the main ore 

 of the mine was taken from the quartzite, which, as well as the lower por- 

 tion of the iron body, was impregnated with gold. The gold was very 



