526 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



carbonate of lead and probably silver. The evidence of extended miner- 

 alization at this point is so strong that it is well worthy of more thorough 

 exploration. In all probability the ore was originally a sulphuret, though 

 containing a smaller portion of pyrites than the Phillips deposit, but so far 

 as examined it has been entirely oxidized. In the White Limestone above, 

 apparently on the same vertical plane with tlie large cavity, an opening has 

 been made on two small bodies of galena, following vertical joining planes 

 in the limestone. It seems probable that the ore which once filled the large 

 cavities was originally deposited along a jointing plane or the plane of a 

 small fault, and that the cavity has been enlarged by secondary alteration. 

 A small fault witli a movement of about twenty feet can be traced along 

 the bed of the shallow ravine which indents the face of the clift'. It is 

 worth)^ of note that all theses planes have a common strike, northeast 

 and southwest, which is also that of the fault on the north face of Love- 

 land Hill ; this may be observed on the opposite side of the canon, about 

 a mile above this point and on a line due southwest from liere. 



Excelsior mine (L). — A little wcst of the Criterion and higher up on the 

 face of the cliff is the Excelsior mine, likewise abandoned, whose position 

 is marked by the skeleton of an old building standing perched on the edge 

 of the cliff, overlooking the precipice below. Here an irregular body of 

 porphyry or porphyrite traverses the White Limestone, which is somewhat 

 contorted at its contact. The mine is opened by a tunnel, on either side of 

 which the eruptive mass crops. But little ore has been developed, but the 

 rocks are deeply stained with iron, and at the contact of the limestone and 

 porphyry is found a little free gold and silver, with copper and iron pyrites. 



The spur of Mount Bross, above these mines, is covered with prospect- 

 holes, the more recent of which are generally in the Blue Limestone. The 

 older prospects, which were made at the time when only gold was sought 

 for, are generally confined to the silicious beds below this horizon. 



Colorado Springs mine. — In the Red amphitheater, higher up the canon, on 

 the south fiice of Mount Bross, is the Colorado Springs mine, which is still 

 being worked, and obtains rich galena ore from tlie lower part of the Blue 

 Limestone, at or near its contact with the Parting Quartzite. The ore body 

 averages two or three feet in thickness. The lower portion of the Blue 



