TOURTELOTTE PARK. 173 
mine ore has made alone the Contact fault at the intersection with vertical 
fractures, some of which have a north-south trend, while others run east 
and west. Pl. XLI, B, is a cross section in a northeast direction through 
the Camp Bird mine, and is extended into the Iowa Chief. It shows the 
ore as actually developed along the Contact fault, and its relation to the ore 
in the Iowa Chief. 
Iowa Chief mine—The working shaft of the lowa Chief mine is called the 
South Camp Bird. This shaft passes through 165 feet of porphyry and then 
15 feet of shale to the Silver fault. Below this fault it passes through 100 
feet of blue Leadville limestone, often dolomized and stained brown, but it 
does not seem to have reached the Contact fault and the main body of Lead- 
ville dolomite. A considerable amount of ore has been taken from this 
mine, some of it of a very high grade. Although on about the same level 
as that of the adjacent Camp Bird mine, the ore is actually at an entirely 
different geological horizon, for while in the Camp Bird it occurs all along 
the Contact fault between the blue limestone and the dolomite of the Lead- 
ville formation, in the Iowa Chief mine it is found along the Silver fault, 
which separates the blue limestone from the overlying porphyry, with a 
small belt of broken shale between. The ore-bearing horizons of the Camp 
Bird and Iowa Chief mines are separated by the Silver Bell fault. This has 
a downthrow on the south side of 200 feet, so that it brings the Silver fault 
down very nearly to the same level as that of the Contact fault in the Camp 
Bird. The Contact fault in the Iowa Chief lies below all the workings, and 
has not been at all prospected, although it is extremely probable that ore 
exists along it, as it does in the Camp Bird. 
The actual occurrence of the ore and the other geological features of 
the mine are shown in Pl. XLI, B, in which the lowa Chief mine occupies 
that portion to the southwest of the Silver Bell fault, at the left-hand part 
of the plate, while the right-hand or northeastern half of the section belongs 
to the Camp Bird. This section has been carefully made, and shows only 
actually developed ores. As seen here, the ore occurs altogether in the 
vicinity of the Silver fault, either in the actual zone of displacement or m 
the dolomite immediately below it, where it has formed along minor slips 
in the limestone parallel to the main fault. This ore is a soft, decomposed, 
pulverulent limestone, containing much barite, with no copper or zine and 
very little lead. There is little or no dolomite in the rocks inclosing the ore, 
