230 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



Long and Derry mines. The Long and Deny workings consist of a number 

 of shafts and tunnels, the former of which the Dana (M-3) and Por- 

 phyry.(E-37) reach the contact through the overlying White Porphyry. 

 Two tunnels on the Faint Hope claim (M-2 and M-4) start in the lime- 

 stone, the latter reaching the contact between porphyry and limestone at 

 183 feet, while the Long and Derry tunnel (E-32) is run in through the 

 porphyry for a distance of 400 feet. Mineral action has here extended 

 down into the limestone body, and ore is found not only at the contact, but 

 in irregular chambers, at considerable depths below it. 



Dikes. Immediately in front of Faint Hope tunnel (M-4) is an out- 

 crop of Gray Porphyry almost identical lithologically with the main sheet 

 of Gray Porphyry. This is part of a vertical dike fifty to sixty feet wide, 

 which can be traced past the Belcher Mine, across Iowa gulch, to the Minor 

 tunnel on Printer Boy Hill. There are three of these vertical dikes, which 

 can be most distinctly seen on the steep slopes of Printer Boy Hill, where 

 in some cases they stand as projecting outcrops, the adjoining rock having 

 been eroded away. They vary from thirty to fifty feet in thickness, and, 

 as well as could be traced on the surface, are nearly parallel and all of the 

 same character of rock. 



For some distance from the Long and Derry mines westward no actual 

 rock outcrops are found on the surface of the ridge. Along its southern 

 slope the presence of the White Limestone and of an included body of 

 coarse-grained quartz-porphyry, somewhat resembling the Josephine Por- 

 phyry, was detected by means of several small prospect holes, too unim- 

 portant to have been indicated on the map. The fine-grained Green Por- 

 phyry is much decomposed and of lighter color than in Iowa gulch. The 

 secondary ridge or shoulder of the main ridge, at the very edge of the map, 

 overlooking Empire gulch, is formed by the Empire north moraine, through 

 which few, if any, prospectors have succeeded in reaching the underlying 

 rock. On the north slope of the ridge, as already mentioned, the White 

 Limestone forms continuous outcrops, crossing which can be detected the 

 vertical dikes which cut the strata at right angles. 



Iowa guich. In the bed of Iowa gulch, as shown in outcrops along the 

 creek at the foot of the Long and Derry grade, and in the Minnehaha (M- 1 5 



