COBIAN IE apis IE EAL. 
DESCRIPTION OF MINES AND PRODUCTIVE LOCALITIES. 
In the preceding chapter the general geology of the Aspen mining 
district has been discussed. Within this district are certain segregated 
areas to which the actual ore production has been almost entirely confined, 
and where most of the mines are located. In the most important of these 
localities the geology has been more accurately determined, thanks to 
the numerous opportunities offered in mine workings, and special maps 
of these localities have been made on the 300-foot scale. 
ASPEN MOUNTAIN. 
One of the areas of greatest production is the north slope of Aspen 
Mountain, between Tourtelotte Park and the town of Aspen. In the east- 
ern limb of the synclinal fold of Aspen Mountain there is a continuous 
series of underground workings, reaching connectedly from the level of the 
town up to the top of the mountain. In this particular region the Contact 
fault between the blue limestone and the dolomite has been considered the 
most favorable place for exploration, and hence this fault, or “‘contact,” as 
it is called, has its outcrop marked the whole distance up the hill by a 
continuous line of tunnels. From this outcrop the workings have often 
gone downward along the dip to a great depth, as is especially the case in 
the Aspen mine. 
Bonnybel mine and Visino tunnel. (See Pl. XL, A).—This mine is situated in a 
small downfaulted block which is bounded on the east by the Bonnybel 
fault and on the west by the Chloride fault. These faults dip to the south- 
west and converge in dip and in trend, so that they probably unite in 
depth and merge into the Silver fault. The downfaulted block is marked 
on the surface partly by the Parting Quartzite beds. he course of these 
beds seems to be comparatively normal from Spar Gulch southward nearly 
to the Bonnybel mine, but here the outcrop is faulted down the hill for 
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