MINE WORKINGS OF IRON HILL. 391 



main ore developments have been in the body of the limestone, extending 

 as much as one hundred feet below its surface, and are opened by the Rus- 

 tin shaft. These and the similar ones in the Silver Wave ground are inter- 

 esting as showing that the ore deposits are by no means confined to the 

 surface of the limestone, as was originally supposed. The bodies are irreg- 

 ular in shape, but have their greatest extent in a nearly vertical direction. 

 The slickensides found on their walls give evidence of some movement, 

 and they were evidently formed by ore currents percolating along cross- 

 joints or planes of fracture in the limestone, having a general north and 

 south direction. The ore is oxidized and does not differ essentially in char- 

 acter from that in the adjoining mines. 



The Stone claim was ingeniously outlined to take in the curving out- 

 crop of the Blue Limestone as it crosses the gulch. The developments on it 

 are mainly on the north side of the gulch, and have as yet opened no con- 

 siderable ore bodies, though the evidences of replacement action are abun- 

 dant. Probably a search below the contact for bodies similar to those of the 

 La Plata might prove remunerative. 



The shaft of the A. Y. mine, above the Stone claim, has developed an 

 extremely interesting occurrence of unoxidized ore, a mass of galena, pvrite, 

 and zinc blende, which was the only one reached in the Leadville region, 

 though unfortunately not accessible, at time of visit. The ore is of low 

 grade in silver, and hence of little value in competition with the more easily 

 reducible oxidized ores. 



Lime and Smuggler. Directly opposite the Rock workings, and at a cor- 

 responding elevation on the north slope of California gulch, are the work- 

 ings of the Lime, Smuggler, and adjoining claims, which, though not very 

 extensive, are sufficient to give evidence of another zone where the lime- 

 stone has been largely replaced by vein material. The minor folds in the 

 limestone are here very sharp, the rock masses near the surface sometimes 

 broken, and the replacement has been somewhat irregular, so that the con- 

 tinuity of the ore bodies is not always evident. Here, as in the Dome 

 claim, a small thickness of White Porphyry separates the intrusive sheet of 

 Gray Porphyry from the contact, as shown in Sections E and F. From 

 the south incline of the Lime to the South Bull's Eye but little ore has 



