MINES OUTSIDE THE LEADVILLE DISTRICT. 523 



Stone, vih\ch forms the surface of the spur between the Cameron and Bross 

 amphitheaters east of the Moose mine, is, like that of the corresponding 

 spur of Mount Lincohi, honeycombed with open cuts, from which appa- 

 rently considerable quantities of ore similar to that of the Moose mine have 

 been taken. So far as observed, the silver deposits in this region have been 

 principall}' confined to the Blue Limestone horizon. 



Dolly varden min^^ qh the eastern slope of Mount Bross, at a little lo^ver 

 level than the Moose mine, is also in the Blue Limestone. Its ore is o-en- 

 erally more oxidized than that of the Moose, and occurs in the body of 

 the limestone, near its contact with a nearly vertical dike of White Porphyry 

 about forty feet thick. The main dike has a strike of between N. 15° E. and 

 N. 30° E., and dips 60° to the northwest. The ore has been found along 

 the southeast face of this dike in a vertical extent of 150 feet, and extend- 

 ing southeastward into the limestone with the dip of the formation to a dis- 

 tance of 100 feet. On the east of the main dike is a second porphyry dike, 

 with a strike nearly east and west and a dip of 45° to the south, which 

 may be simply a branch of the main dike. On the west side of the main 

 dike as yet no considerable amount of ore has been discovered. 



In the little valley on the southeast slope of Mount Bross, known as 

 Mineral Park, is the tunnel of a company which was organized during the 

 prosperous times of this region with the avowed intention of piercing the 

 mountain to strike the source of the rich dej^osits of the Moose and other 

 mines. It was not visited by the writer, hence an exact description of the 

 rocks through which it has passed cannot be given, but it deserves mention, 

 as illustrating the ])ernicious habit among* western miners of spending large 

 sums in running tunnels through the solid rock with no sounder basis of 

 hope than the chance of striking some unknown rich deposit. This tunnel 

 is said to start in quartzite and to have been driven about seven hundred 

 feet. Whether it commences at the Parting Quartzite or at once in the 

 Lower Quartzite is a matter of comparatively little importance. It starts, 

 at all events, below the horizon of the Blue Limestone, and therefore can 

 b}' no possibility strike any of the ore bodies contained in that stratum. As 

 will readily be seen by reference to Section L of Atlas Sheet X, the tunnel 

 will soon, if it has not already done so, reach the crystalline rocks of the 



