BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 467 
GEOLOGICAL FEATURES. 
The general country rock of the mine is the conspicuously porphyritic Pikes 
Peak granite prevalent in this part of the district. Here, as elsewhere, this granite 
often exhibits a distinct gneissoidal structure. The northern portions of levels 1, 2, 
and 3, and perhaps also of levels 4 and 5, extend into the breccia, the contact 
between the granite and the breccia being irregular, but distinct. On level 1 the 
breccia is first seen in the main drift about 425 feet north of the shaft. The con¬ 
tact, which is followed for about 500 feet by the drift, runs in a general north- 
northwest direction for about 300 feet and then turns nearly due north toward 
the Burns shaft of the Portland mine. On level 3 the contact crosses the main 
drift about 600 feet north of the shaft, and has been drifted on for about 500 feet 
northward from this point. Its general course is similar to that on level 1, and its 
dip, as shown by the relative positions of these two levels, is easterly, ranging from 
65° on the south to 85° on the north. The breccia seen in the Strong mine presents 
no unusual character and is similar to that already described in the southwestern 
part of the Portland mine. 
There are two important phonolite dikes in the Strong mine. The larger and 
better known of these, while somewhat irregular in trend, has in the main a north- 
south course. It has been identified on all of the levels and extends through the 
Strong claim, entering near the middle of the south end line and passing out near 
the northeast corner. It thus cuts both granite and breccia. Its general dip is 
that of the Strong lode, the two being sometimes coincident for several hundred 
feet. When not coincident the phonolite dike usually lies a tew feet east of the 
lode, though in one place, on level 6, it lies immediately west of the ore. The average 
width of the dike is about 7 feet. It is composed of the altered greenish-gray 
aphanitic phonolite, with platy parting parallel with the walls, that constitutes the 
common dike facies in the Cripple Creek mines. 
The second phonolite dike, known as the “ cross dike,” derives its name from the 
fact that its course crosses that of the first dike. It is apparently more irregular 
and less persistent than the main dike, its course, as observed on different levels, 
varying from west-northwest to north-northwest. The dip is in general to the 
southwest. On level 1 the cross dike is exposed in breccia in the right-hand branch 
of the main north drift, about 800 feet north of the shaft. Its course as exposed 
for a length of 70 feet is far from straight, but seems to be in general about west- 
northwest. It was not noted in the left-hand branch of the drift and may not 
cross the granite-breccia contact (PI. V, p. 26). On level 3 the dike is in granite 
and intersects the main phonolite dike 575 feet north of the shaft. There is no 
evidence at the crossing that one dike is older than the other, and they were probably 
intruded simultaneously. The dip of this portion of the cross dike, as indicated by 
its relative positions on levels 1 and 3, is southwest at an angle of about 40°. On 
level 4 the dike could not be seen, but on level 5 it is encountered about 600 feet 
north of the shaft and followed for some distance by the main drift. Its course 
here is roughly north-northwest. It is not altogether certain that this is the same 
cross dike known on the upper levels. If it is, it indicates not only a pronounced 
