394 GEOLOGY JLXD MINING INDUSTRY OF LEADVILLE. 



from below. In general outline the bodies seem pear-shaped, with the 

 taper toward the top. Similar bodies are found around the Silver Cord 

 shaft, also having a northeast trend, and, as the map shows, in a direct line 

 with those in the Silver Wave and Grand View claims. East of the Silver 

 Cord shaft a steeper dip in the formation comes in, which may be a contin- 

 uation of the fold already noticed in the South Bull's Eye. It seems, then, 

 that before the dynamic movement in this region there was a certain amount 

 of fracturing of the beds, not, however, accompanied by any considerable 

 displacement, and that along these planes of fracture the ore currents have 

 penetrated into the body of the limestone, the ore deposition or replacement 

 acting from their walls outward. 



In the Silver Wave claim was also seen a freshly opened cave, one of 

 the few that are found in the Leadville mines, and which is of interest as 

 bearing on the generally-advanced theory that ore bodies in limestone are 

 necessarily deposits in pre-existing cavities. It was somewhat funnel-shaped 

 toward the top, about twenty-five feet in horizontal diameter, and contained 

 no ore. Its walls, which had the wavy surface common to water-worn lime- 

 stone, were covered with a thin coating of fine reddish ooze or slime. An 

 examination of the walls showed that these were in part of unaltered lime- 

 stone and in part of ore and vein material, which could not be distinguished 

 from each other until the coating had been removed. It was thus evident 

 that the cave was of comparatively recent formation, made by the percola- 

 tion of surface waters and carved out of limestone and ore body indiffer- 

 ently ; hence, that it is entirely posterior to the deposition of the ore, which 

 was formed before surface waters, as the term is generally understood, 

 could have reached to this depth. 



iron mine proper. The underground workings of the group of claims 

 which are exploited from the various shafts and inclines of the Iron mine 

 cover an area of about twenty -five acres, being the most considerable of any 

 single mine in the district. They have been driven a distance of over fif- 

 teen huadred feet along the contact eastward from the outcrop, or rather 

 from the fault line, since at the peculiar eastward bend of the fault plane 

 in the Iron and Iron Hat claims the limestone does not actually come to the 

 surface. 



