422 GEOLOGY AND MINING INDUSTKY OF LEADVILLE. 



by narrowings of the ore body cannot be determined. Pay ore was mostly 

 in the form of sand carbonates, slightly impregnated with iron oxides, and 

 in comparatively thin sheets, having a maximum thickness of about two or 

 three feet. Connection was made from the second level to the end of the 

 JEtna incline, to prevent the owners of the latter mine from following their 

 ore shoot farther into the Carbonate ground, but is now closed up. Between 

 the second level and the third and fourth is a large piece of comparatively 

 barren ground, as indicated by the outlines of the ore body given on the 

 map. These outlines, it must be borne in mind, are, from the necessity of 

 the case, considerably generalized, it being impracticable to obtain accu- 

 rate data with regard to their definite limits in the present abandoned con- 

 dition of the workings. 



One of the richest ore bodies in the mine was found immediately adjoin- 

 ing the incline on the north, between the third and fifth levels, occupying a 

 slight depression immediately adjoining the crest of the main fold in the 

 limestone. This ore body was in places two sets high (some fifteen feet 

 thick), gradually thinning as it approached the crest of the fold, and to the 

 northeastward spreading out in a thin and comparatively continuous sheet 

 of sand carbonates. In the drift on the fourth level north, a body of unal- 

 tered limestone rises up in the floor, cutting off the ore about twenty feet 

 from the incline; beyond this point ore is only found in detached bodies to 

 the west of the drift, while to the east it extends in practically continuous 

 sheets to the lower levels, gradually taking a steep easterly dip. The north- 

 ern extension of the drift, after passing through a considerable stretch of bar- 

 ren contact, cuts several small, unimportant ore bodies, which form a con- 

 tinuation of those developed in the lower levels, and at its extremity was 

 being run at the time of visit in solid limestone. 



The fifth level is cut for a short distance from the incline in the lime- 

 stone of the fold, then passes through the clay contact, showing consider- 

 able slickensides. The contact here is somewhat typical, showing first a 

 blackening of the limestone by a certain amount of impregnation by man- 

 ganese and iron oxides; above this, iron-stained clayey matter, containing 

 the usual development of Chinese talc; and still above, a thin irregular body 

 of quartzite (Weber Shales), followed by normal White Porphyry. The 



