TOURTELOTTE PARK. IR TEC 
In the O. K. such a mineralized zone has been followed up across the blue 
limestone quite to the shale, and there is rich ore lying immediately under 
the shale. The ore in these steeply dipping shoots is crushed and broken 
blue limestone, more or less dolomized, but with blue limestone on both 
sides a short distance away from the vein, and it contains less barite and 
more lead and silver than do the great masses of low-grade ore which are 
found everywhere along the Contact fault. The occurrence of the two 
varieties of ore under different conditions suggests two slightly differing 
periods of mineralization. 
In the region occupied by these mines the porphyry sheet, which in 
the whole southern part of Tourtelotte Park and on Aspen Mountain lies 
very close to the Silver fault, seems to have cut up abruptly to the south 
across the shales, so that the amount of shales overlying the blue limestone 
is greatly increased and the porphyry disappears altogether. Thus the 
Last Dollar shaft, which is 465 feet deep, passed through 35 feet of glacial 
drift, about 220 feet of Weber shales, and then crossed the Silver fault into 
the blue limestone. 
Little Rule tunnel— The Little Rule tunnel starts just above the Contact 
fault, in a place where the original blue limestone has been entirely altered 
to dolomite. It runs east, following a bedded vein which contains a great 
deal of barite, but not enough lead and silver to make it profitable ore. 
The rock on both sides of this vein, above and below, is altered to dolo- 
mite, or “‘short lime,” and is considerably iron-stained, especially near the 
vein. Near the end of the tunnel the rock, and with it the vein, becomes 
broken and shifted about. A little farther in the Sarah Jane fault is 
crossed, and the Weber shale, which lies on the east side of the fault at 
this point, is entered. There is not much mineralization along the Sarah 
Jane fault at this point, and very little pay ore has been found in the 
workings. 
The Sarah Janemine—The Sarah Jane workings are mostly in a zone of 
shattered and highly altered rock in the vicinity of the Sarah Jane fault. 
Although much of this rock was originally blue limestone, it is now all 
dolomized. The ore, which is all oxidized, occurs in pipelike shoots, 
which run up through the altered rock. It is highly siliceous, as is also 
the rock in its immediate vicinity. Another peculiarity in the ore is the 
presence of a large amount of calcite. 
MON XXXI——12 
