ASPEN MOUNTAIN. 159 
Enterprise tunnel_— [he Hnterprise tunnel runs in drift to the blue lime- 
stone, and through this to the Contact fault. A drift runs from this point 
northeast and southwest on the Contact fault, which shows slickensiding, 
brecciation, and watercourses filled with mud. These workings have 
developed some ore along the Contact fault, in shoots which probably 
belong to the same system as those of the A. M.and 8. Ore is also found 
along the same shoots in the Little Nell tunnel and the Thousand-and-one 
incline. 
Argentum-Juniata mine——In this’'mine the formations are the same as in the 
A.M. and 8., but they do not outcrop, since they are entirely beneath 
Roaring Fork Valley and are deeply covered with drift. This mine affords 
one of the most favorable means for determining the structure which lies 
under the river valley and which is hidden by the glacial material, and from 
its workings, and those of the Mollie Gibson on the other side of the valley, 
it appears that there is no great complication in the space between Aspen 
and Smuggler mountains. The Argentum-Juniata workings are run on the 
Contact fault between the blue limestone and the dolomite, which, with the 
other formations, have a steep but comparatively uniform dip. There is 
some slight faulting shown in the mine, but none which has any very 
heavy displacement, if we exclude the Silver fault. This fault is exposed 
between the shale and the blue limestone at one or two points by cross 
drifts running west from the Contact fault, and is characterized by a thick 
breccia of porphyry, shale, and limestone, and by open fissures and water- 
courses in the limestone, parallel to the main fault. Besides the Silver and 
the Contact faults the disturbance consists mostly of a series of parallel 
fractures, which have some slight displacement. These strike northwest 
and have a steep southwest dip. Along some of these fractures much water 
pours into the mine. An interesting feature is the alteration of the lime- 
stone and dolomite along some of the zones of fracture to a soft, black 
material, which so closely resembles the softened Weber shale that the two 
can not easily be distinguished. 
The ore has been found chiefly along the Contact fault, but irregularly 
distributed. It is not yet determined whether the system of northwest 
fractures has any reference to the localization of the ore deposits. The ore 
is an alteration of limestone or dolomite, is generally stained brown by iron 
oxide, and carries considerable barite. 
