ASPEN SPECIAL MAP. all 
Quartzite is exposed on the top of the hill, and as the rocks dip more 
steeply on the east side of the hill than does the slope of the hill itself, 
there are found below the Parting Quartzite outcrop the dolomite and blue 
limestone of the Leadville formation On both sides of these Leadville 
rocks, and separated from them by the cross faults, is the Silurian dolomite. 
At this point the block presents in cross sections the aspect of being down- 
faulted relatively to the blocks on both sides, as is shown in Section B, 
although on the west side of the hill, as shown by the outcropping Cam- 
brian quartzite, the block has the same general movement as its neighbors, 
being downthrust from the block next north, and upthrust relatively to the 
block next south. 
In one of the parallel east-west faults of West Aspen Mountain, which 
is cut by the Falco tunnel, some ore is found. These minor faults, there- 
fore, are also probably older than the ore deposition. 
Pl. II is a view of the end of West Aspen Mountain, taken from the 
valley near the Roarmg Fork and looking southwesterly up Maroon Creek. 
The outcropping rocks, as best seen in the case of the Silurian dolomite on 
the extreme north face of the mountain, have the same angle of dip as 
does the mountain itself, while the somewhat steeper faults run up the 
mountain in the shallow gulches or depressions lying between the out- 
cropping, nearly parallel ridges, which are seen in the picture. In the 
foreground of this plate is the Roaring Fork, while in the distance, on 
the west side of Maroon Creek, are seen the upper Triassic beds and the 
rocks of the Gunnison formation, with the Dakota sandstones forming 
the top of the ridge as it slopes away gently to the west. 
Silver fault —The Silver fault is developed continuously by mine workings 
through the whole of its course across the area of the Aspen special map. 
It is marked by a thin zone of brecciated material, whose composition often 
shows that some of it has been dragged from a distance, and by polished 
and striated walls of hard rock. On Aspen Mountain there lies always to 
the east of the fault the blue Leadville limestone, and to the west the sonata 
thick sheet of porphyry. Between the porphyry itself and the fault there 
is usually a zone of crushed and broken shale, often mixed with porphyry, 
which is never very thick and sometimes is almost entirely absent. On 
Aspen Mountain the Silver fault is not exactly parallel with the bedding, 
for in the northern part of the mountain it cuts deeper into the beds, so 
