412 GEOLOGY AXD MINING INDUSTEY OF LBADVILLE. 



Southwest slope of Carbonate h:ii. — The detailed map of Carbonate Hill (Atlas 

 SheetXXVIII), while including the principal mines, covers only the northern 

 portion of the western slopes. For the geology of the sonthern portion, 

 in which as yet no ore bodies of importance have been developed, refer- 

 ence must be had to the general map of Leadville (Atlas Sheet XIV), on 

 which the limits of the detailed map are indicated. South of these limits 

 the Prospect incline, the Rosebud and Deadbroke tunnels, on the north 

 side, and the Jordan and Swamp Angel tunnels, on the south side of Cali- 

 fornia gulch, follow the upper surface of the Blue Limestone. While this 

 surface shows evidence of mineralization in the characteristic iron-stained 

 material generally found at the contact and in the frequent occurrence of 

 the so-called Chinese talc, supposed to be the product of the alteration of 

 the porphyry by mineral solutions, it has thus far been found comparatively 

 barren of rich ore bodies. In the Prospect incline, about three hundred and 

 seventy-five feet from the mouth, the surface of the limestone, which had 

 hitherto been wavy, as it is generally found, suddenly drops down almost per- 

 pendicularly for 125 feet; 60 feet farther on in the line of the incline, how- 

 ever, the limestone is found fol'owing its normal dip to the eastward. This 

 is apparently a very sharp fold in the limestone, accompanied by a certain 

 amount of faulting. It is approximately on the line with the sharp fold 

 which will be described hereafter as running through the Carbonate and 

 Yankee Doodle mines, but the accumulation of rich ore, which in these 

 mines is found above the fold, is here wanting. 



The only actual rock exposure in this region is that of the White 

 Limestone in the quarry on tlie north side of California gulch. From a 

 prospect hole sunk by placer miners in the bed of California gulch, above 

 the flume, casts of a RhynconeUa, in a sandy white limestone, are obtained. 



Of the two porphj^ry sheets which are indicated here, the upper one, 

 near the base of the Blue Limestone, has been traced from tlie Irish Giant 

 shaft to the Silver Star, and from that, a little beloAv the John Harlan, across 

 the gulch to the Logan and Broadway shafts, on the south side. This is 

 evidently the same sheet which to the north occurs near or at the base of 

 the Blue Limestone and in the Henriett and Waterloo claims cuts up across 

 it into the White Porphyry. The lower sheet of porphyry oscurs in the 



