248 geologTl and mining industry of leadville. 



North Iron Hill. — From the Codfish Balls shaft northward to Stray Horse 

 gulch the line of the Iron fault is somewhat indefinite, the miners who 

 sunk the few shafts not having found any valuable ore bodies at the con- 

 tact and having confounded the limestone, which is here bleached quite 

 white, with the overlying porphyry. In the angle between the Iron fault 

 and the Adelaide cross-fault, as shown by the workings of the Argentine 

 and Adelaide mines, the formation dips to the southeast, so that successive 

 outcrops of White Limestone and Lower Quartzite are brought to the surface. 

 The structure at this point, which will be explained in detail in Part II, 

 Chapter II, is still further complicated by the intrusion of minor sheets of 

 Gray and White Porphyry, which have split up the Silurian formation, and 

 by the crossing of the main sheet of White Porphyry down to the horizon 

 of the Parting Quartzite across the basset edges of the Blue Limestone. 

 The principal mineralization has here taken place at the contact of this 

 White Porphyry with the Parting Quartzite, instead of, as in other cases, 

 on the surface of or in the Blue Limestone. 



AREA BETWEEN IRON-DOME AND CARBONATE FAULTS. 



Carbonate fault. — Carbonate fault has a general direction a little more to 

 the east of north than Iron fault. Its upthrow is likewise to the eastward, 

 and the displacement has a probable maximum in the bed of California 

 g'ulch, where Silurian beds are proved by shaft developments to come 

 in contact with White Porphyry. On the southern slope of Carbonate 

 Hill its plane is actually proved in the shafts of the ^tna and Yankee 

 Doodle mines. Here its movement is only about two hundred feet; but a 

 second fault is found crossing the Glass-Pendery claim, the amount of 

 whose movement, which is also an upthrow to the east, is not known, since 

 the contact has not been reached on its west side. This fault apparently 

 joins the Carbonate fault before reaching California gulch. Northward the 

 movement of the Carbonate fault gradually decreases and is partially dis- 

 tributed among some smaller faults and folds. In this portion its actual 

 plane has not been proved; and it is very possible that it does not extend 

 as a continuous fault as far as indicated on the map. Indeed, in tlie 



