LITTLE ANNIE MINE. 205 
Centennial tunnel— The Centennial tunnel started in porphyry above the 
Dubuque and crossed eastward through the Castle Creek fault into the 
Cambrian quartzite. At the end of the tunnel a raise was made up to the 
Silurian dolomite. 
Gray Carbonate tunnel —On the hill above the Centennial and Dubuque tun- 
nels the Gray Carbonate tunnel runs into Silurian dolomite, and there 
exposes a small amount of ore, some of which has been shipped. 
Yopsie tunnel— The Yopsie tunnel starts on the crest between Queens and 
Yopsie gulches. It runs in gray grits and in the pure gray limestone 
belonging to the base of the Maroon formation for a considerable distance, 
following a perfectly distinct vertical vein. This vein is of barite, often 
copper stained, and in the rock on both sides there are many parallel 
fractures. Both vein and fractures trend northwest, parallel to the Castle 
Creek fault. The heavy spar, however, is practically barren of valuable 
minerals, and thus affords another proof that the barite and the metallic 
sulphides were not necessarily deposited at the same time. 
LITTLE ANNIE MINE. 
The Little Annie mine is located on the Castle Creek fault, a short 
distance from the southern end of the area mapped. Its workings are in 
porphyry and shale on the west side of the fault, and it also crosses the 
fault into the Silurian dolomite. West of the main fault a series of just 
such dependent breaks as were noticed in the Dubuque tunnel exist and 
are shown in the cross section on Pl. XLIII, D. The fault between 
porphyry and shale has been called throughout the district the Annie. 
The shales on the west side of the porphyry are generally disturbed, 
especially close to the fault, being bent and squeezed between the minor 
slips, but farther away their attitude becomes more uniform. 
In the lower levels of this mine the ore is a sulphide of lead, zinc, and 
silver, with a considerable amount of barite. The galena is sometimes 
beautifully crystallized, and the silver is often found native. The ore 
occurs chiefly in the immediate vicinity of the Castle Creek fault, but on 
the west side of it, being developed along many of the slight faults and 
fractures in the shale and porphyry. Some was also found in the dolomite 
on the east side, but these deposits were apparently not so extensive. In 
the upper levels the ore is oxidized. 
