502 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



Both tunnel and shaft are driven through Gray Porphyry to the contact, 

 the upper White Porphyry being here wanting. No limestone is struck in 

 either, but a winze sunk a short distance from the mouth of the shaft found 

 it, as did the Highland Mary (G-55) and Curran (G-56) shafts close by, 

 which found some vein material, but no ore. Vein material rises rapidly 

 in the floor of the tunnel as it approaches the shaft, and the latter is sunk 

 in it 1 70 feet below the tunnel level. The lower surface of the porphyry 

 sheet has a dip to the northeast, which is also seen in the eastern portion 

 of the workings beyond the line of the section, while in the southwest 

 workings there is a dip westward. In the Chemung (K-5) tunnel, which 

 is driven 400 feet, along the contact of Gray and White Porphyries and 

 then in Blue Limestone, in a southeasterly direction, from a point just 

 below the road about seven hundred feet southwest of the mouth of the 

 Highland Chief tunnel, the limestone at the end is found to be dipping 

 westward. It thus appears that there is a slight ridge or lateral fold in 

 the formation, which is shown on the map by the curve in the strike of 

 the formations. The section, whose line is taken along the crest of this 

 fold, shows at right angles to it a more pronounced folding, forming an 

 anticlinal and synclinal structure parallel to the South Evans anticline, 

 which is necessitated by the intersections of formation lines obtained in 

 the Highland Chief and Eliza (G-58) shafts. The intermediate outcrops 

 are obscured by the moraine material or Wash, left on the shoulder of 

 the hill by the South Evans glacier. The section shows the rounded 

 outlines of rock surface left under the Wash by this glacier and the abrupt 

 slope below the Eliza shaft produced by later erosion. A dike of Gray 

 Porphyry, running northeast and southwest, is cut in the south drifts from 

 the second level of the Highland Chief mine, but does not seem to be con- 

 tinuous, as it is wanting in the southwest workings on the tunnel level. It 

 has evidently the same irregular character that has been seen in similar 

 transverse bodies on Carbonate and Iron Hills, and, like them, has evidently 

 had a favorable influence on the concentration of ore. The vein material 

 of this mine is very silicious and resembles the porous hard carbonate 

 described in Carbonate Hill, but carries less iron ; the cavities contain cerus- 

 site and chloride of silver. The ore is relatively rich, many lots averaging 



