254 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



Eastern rim. The Blue Limestone, which is largely replaced by vein 

 material, comes to the surface on the eastern rim of the basin along the 

 foot of the steeper slope of Yankee Hill. It is found directly under the 

 Wash in the Cordelia Edmonston and adjoining shafts. The Birdie Tribble 

 (P-42), at the very edge of the basin, found five feet of porphyry above 

 the vein material and limestone. In the shafts of the Kennebec (P 55) 

 both Gray and White Porphyry are passed through before reaching the 

 limestone, and a sheet of porphyry six feet thick was also cut in the body 

 of the limestone. The Chieftain tunnel and incline run in a southeasterly 

 direction 360 feet through vein material and limestone, finding the Iron 

 fault with granite on its farther side at the end. The limestone here shows 

 the effects of a movement against the fault plane, being compressed into short 

 sharp folds and much metamorphosed. There is a general tendency, how- 

 ever, to dip to the northwest; and it is probable that the extremity of the 

 incline is in the White Limestone, although lithological indications are here 

 extremely deceptive, owing to the alteration to which the rocks have been 

 subjected. The Scooper shaft (P-44), a little to the south of the Chieftain, 

 passed through 20 feet of Gray Porphyry and 5 feet of White Porphyry 

 before reaching the Blue Limestone. The contact here stands so nearly 

 vertical that it was supposed by the superintendent to be a fault. This 

 supposition was rendered more probable by the fact that the line of this 

 contact runs in a southeasterly direction. It is probably, however, only an 

 exceptionally steep dip on this side of the basin. South of this the Del 

 Monte (P-45) shaft is in Gray Porphyry. The Hard Cash (P-46) shaft 

 is in vein material. The I^airplay (P 34) is still in White Porphyry, below 

 the Blue Limestone. The upper White Porphyry, so thin in the Scooper, 

 disappears entirely a little farther south, being altogether wanting in the 

 Rarus shaft (P-61); or, as it might be considered, it is found entirely 

 below the upper sheet of Blue Limestone. 



The fact that the Blue Limestone is split into two sheets by the White 

 Porphyry is shown in the shafts east of the Rarus in Stray Horse gulch. 

 The Indiana shaft (P-53) finds the limestone directly under the Wash. 

 East of this the Young Caribou (P-59) finds White Porphyry under the 



