MINES OF BATTLE MOUNTAIN, EAST GROUP. 
437 
from the present underground development. The southern boundary of this latite- 
phonolite, on all levels, lies along the northern edge of the great Hidden Treasure- 
Captain ore zone, and there can be little doubt that the presence of the latite-phonolite 
has determined the position and particularly the northern limit of this ore zone. 
The adit level, from a point near the Wisconsin shaft, extends northward for nearly 
I, 200 feet through this body of latite-phonolite before again entering the breccia. 
It is noteworthy that the ore of the Colorado City and Hawkeye shafts occurs in the 
breccia just north of this latite-phonolite, the latter occupying the relatively barren 
ground between this ore and the Captain-Hidden Treasure ore zone. On the same 
level a west crosscut past the No. 3 shaft is entirely in this body of latite-phonolite, 
which is the prevailing rock in the vicinity of the Lost Anna shaft. The same large 
irregular mass of latite-phonolite is encountered on the lower levels just northwest 
of the Hidden Treasure and Captain stopes. The 500-foot and 1,000-foot levels, 
however, are the only ones which explore the latite-phonolite for any considerable 
distance. The distribution of the latite-phonolite on the 500-foot level, so far as 
known, is shown in PI. XXVIII. On that level a crosscut west of the Anna Lee 
shaft cuts through about 300 feet of latite-phonolite, which, as the surface map 
(PI. II, in pocket) shows, is probably an offshoot from the main body to the north. 
On the same level a crosscut west from the No. 3 shaft, after passing for about 450 
feet through latite-phonolite, is continued for about 70 feet in sj^enite. This is 
probably the same mass as that mapped on the northern slope of Battle Mountain 
(PI. II). The contact between this syenite and the latite-phonolite is indistinct, 
and the one rock probably grades into the other. 
In September, 1903, the drift north from the No. 3 shaft was about 700 feet 
in length and all in the latite-phonolite. The eastern contact of the massive rock 
with the breccia has apparently a westerly dip, for while on the adit level the latite- 
phonolite extends at least 400 feet east of the No. 3 shaft, on the 1,000-foot level 
the contact lies from 50 to 75 feet west of the shalt, which on this level is in breccia. 
The latite-phonolite (biotite trachyte) just considered is the “ mica-bearing 
andesite” of Cross," which he described as occurring on Battle Mountain, but 
omitted from his‘geological map on account of the difficulty of determining its 
exact boundaries. 
East of the No. 2 shaft and the No. 2 vein is a part of the Portland property 
that has as yet had very little underground exploration. The geological map (PI. 
II, in pocket) shows that there is exposed at the surface just east of the Burns 
shaft, stretching northeastward along the slope of Battle Mountain and eastward 
to Goldfield, an exceedingly irregular area of latite-phonolite. This phonolite is 
met with underground on the adit level, extending from the portal to a point about 
200 feet north of No. 2 shaft. In places, particularly near the shaft, it is fresh and 
approaches syenite in texture. As in the case of the andesite, its contact with the 
breccia on the northwest is obscured by shattering and mineralization, so that prac¬ 
tically nothing can be made out of the geological relation of the two rocks. Below 
the adit level the phonolite is known to occur in the old Scranton workings and on 
the 220-foot Portland level. It formed the general country rock of part of the 
a Geology and mining industries of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, 
pt. 2, 1895, pp. 75-76. 
