MINE WORKINGS OF IRON HILL. 389 



minerals, or those of less frequent occurrence, are sulphate of lead or 

 anglesite, pyromorphite, minium, zinc blende, and calamine. Native sul- 

 phur is found in one instance as the result of the decomposition of galena, 

 and native silver formed by the reduction of chloride. 



MIN'E WOKKIXGS. 



The principal mine workings in the area represented on the Iron Hill 

 map may be divided into the following groups, commencing at the south: 



1. The Rock and Dome. 



2. The La Plata and Stone. 



3. The Liuie and Smuggler. 



4. The Silver Wave and Silver Cord, including the South Bull's Eye. 



5. The Iron mine proper, including the North Bull's Eye. 



Rock and Dome. These two claims are owned and worked by the Iron 

 Silver Mining Company. The former is opened by a tunnel running south- 

 ward on the strike, the latter by an incline running eastward on the dip. 

 The ore bodies thus far developed in either mine are found near the sur- 

 face of the hill and may belong to the same bonanza, if the same north- 

 easterly direction of ore shoots prevails here as does on Iron Hfll. On the 

 hillside, at the present mouth of the Rock tunnel, was formerly an actual 

 rock outcrop, consisting largely of hard carbonate, from which the mine 

 derived its name and where the first ore in place was found in this region. 

 From it were no doubt derived the heavy fragments which caused so 

 much annoyance to the early gulch miners. 



From this tunnel level the ore has been followed along the contact of 

 limestone and porphyry a certain distance upward or toward the outcrop, 

 but mainly eastward in the trough of a fold and then downward on the dip 

 The workings have also been pushed southward with the intention of mak- 

 ing a connection with the Dome workings. Beyond the crest of the fold 

 to the eastward the contact has thus far proved comparatively barren, but 

 at the lower extremity of the Rock incline ore has been found which may 

 be the precursor of a second ore shoot. 



In the Dome the rich ore has thus far been found near the mouth of 

 the incline, in very considerable thickness and with a remarkable develop- 



