250 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



on the crest of the ridge, which reached it after passing through the over- 

 lying Wliite Porphyry.^ 



Emmet fault. — The Robert Emmet tunnel (0-45) starts in near the 

 contact of Gray Porphyry and overl3'ing White Porphyry. A winze was 

 sunk in the tunnel, from which a drift to the west has cut the Emmet fault, 

 a short cross-fault, by whose movement a little triangular block of ground 

 is lifted up on the westward. Parallel with this fault is a slight anticlinal 

 fold, along the axis of which the Columbia tunnel runs in on the contact 

 and finds the formation dipping away to the right and left, but more steeply 

 to the westward. The Blue Limestone is found in actual rock outcrop on 

 the bank of the gulch below this. The Crescentia shaft, a little west of the 

 Columbia, had reached the Gray Porphyry under the White Porphyry at a 

 depth of 335 feet. It is probable that this body of Gray Porpliyry thins 

 out to the west of this. 



As to theexact line of the continuation of the Iron fault on the south 

 side of the gulch, if it extends so far, no data have yet been obtained, nor 

 can it be definitely stated whether Crescentia shaft is to the east or to the 

 west of tliis line. The dip of the formation west of the Columbia tunnel 

 . is steep enough to account for the contact not yet having been reached in 

 this shaft at a depth of 335 feet.^ 



Graham Park. — Qn the steep west slope of Iron Hill toward Graham gulch 

 the White Porphyry is probably at its thickest in this area. The Blind 

 Tom shaft has been sunk in it to a very considerable depth, though the 

 exact depth could not be ascertained. The City of Paris shaft and bore- 

 hole are said to have passed through 200 feet of Lake beds and GOO feet of 

 White Porphyry below them. Other shafts on the Carbonate Hill side have 

 reached depths of 500 feet and are still in the porphyry. The Devlin shaft, 

 however, on the northwest slope of Iron Hill, reached the contact at 200 feet 

 and the Highland Mary (P-52) found it at 175 feet. These facts furnish 

 a direct evidence of what might have been assumed by analogy, that the 



' Since tlie close of field-work contact lias been reached in the Vining at 317 feet and in the Little 

 Eosie at 375 feet, in the latter of which the fornjatiou is said to dip 30^ to the southwest, thus con- 

 firniiug the deductions made from the relations of the two porphyry bodies. 



^ Since the close of field-work a westerly-dipping contact is said to have been reached by a drift 

 east from the bottom of the Crescentia shaft, at a distance of 300 feet. 



