506 GEOLOGY AND MINING INDUSTRY OF LEADYILLE. 



LITTLE ELLEN HILL. 



On Little Ellen Hill the Blue Limestone has been found to be replaced 

 to a considerable extent and some argentiferous lead ore has been obtained 

 from it; but present explorations cover only a small proportion of its area. 

 The principal mines are the Virginias and Little Ellen. The Virginius 

 (G-24) is opened by a tunnel run southwards along the strike of the for- 

 mation from the north side of the hill, facing Big Evans gulch. The lime- 

 stone is largely disintegrated and in the condition of lime-sand. The vein 

 material, as usual an impure iron oxide, is very silicious. Galena is thickly 

 scattered througii it. but the ore is of rather low grade in silver. The 

 tunnel is 250. feet long, and drifts from it have been driven eastward 150 

 feet on the dip. On the hill above, in the Cleveland (G-27), 15 feet of vein 

 material, carrying galena, are found above the limestone, and at a depth of 

 30 feet in the limestone a cross-cutting body of Gray Porphyry, which is 

 also cut in the Last Chance (G-31) shaft, immediately below the Wash. 

 The other shaft (G-30) of the Last Chance finds Parting Quartzite below 

 the Wash. The Australian (G-28) and Tenderfoot (G-26) also find vein 

 material at the contact. 



The Little Ellen mine, higher up and on the slope of the hill facing 

 South Evans gulch, finds a very large body of low-grade lead ore at the 

 same horizon, where the strike has changed to east and west. This con- 

 tact is traced eastward through the Lulu, Gnome, and Alps workings, show- 

 ing considerable replacement action, bixt as yet no large ore bodies. 



BREECE HILL. 



In the large area lying between the regions above described and Iowa 

 gulch there is an immense development of igneous rocks, and, on the 

 theoines deduced from the studies made in this region that there is a direct 

 connection between igneous action and ore deposition, or rather that the 

 latter is more abundant where the former has been most active, this area 

 should contain large deposits of ore. Unfoilunately there is little else than 

 theory upon which to base this assumption. The ore horizon throughout 

 the greater part of the area is so deeply buried beneath the surface that, in 

 the uncertainty that exists as to how deep it may be necessary to sink a 



