MINES OF BATTLE MOUNTAIN, EAST GROUP. 
457 
GEOLOGICAL FEATURES. 
Like so many of the large mines near Victor, Stratton’s Independence is partly 
in granite and partly in breccia. In general petrographical character these rocks 
are identical with those described in the Portland mine, though, as the Independence 
workings do not extend so far into the breccia, certain facies of this rock, such as 
those in the vicinity of the Captain lodes, do not occur in the more southerly mine. 
While in the Portland mine the contact between the granite and breccia is generally 
convex toward the northeast, in the Independence it is concave (PI. V, p. 26). 
In the Portland the granite projects into the breccia as a steep promontory; in the 
Independence the breccia lies in the curved embayment on the east side of this 
jutting point of granite. The benched form of the contact surface, already described 
in the Portland, is also well exhibited in the northern part of the Independence 
embayment. (See fig. 61, p. 458.) The Independence shaft is sunk in the granite, 
the collar being very close to the granite-breccia contact as exposed at the surface. 
The drifts running north from the shaft at successivelv lower levels cut the contact 
at increasing distances from the shaft (fig. 62), the successive increments of dis¬ 
tance being such as to show that this portion of the contact has a general dip of at 
least 60° N. or NE. Farther north, however, the dip becomes considerably less than 
this above level 5 and considerably more below it. There is thus in the north¬ 
western part of the mine, adjoining the Strong and Portland mines, a notable 
bench-like flattening of the granitic surface against which the breccia rests (PI. V, 
p. 26 ; fig. 62, p. 459). As a consequence of this, the productive northern portions of 
the levels above the fifth are chiefly in breccia, while below level 5, the workings are 
chiefly in granite. This fact may be exhibited with greater clearness by noting 
the relation of the Independence lode to the country rocks on different levels. On 
levels 1, 2, and 3 the lode, in granite near the shaft, soon passes into breccia and 
continues in this rock past the Portland line. On level 4, the Independence lode 
passes into breccia about 250 feet north of the shaft, and thence northward remains 
wholly in this rock. The granite, however, on this level appears again in the 
Strong drift, about 325 feet west of the Independence vein (PL V, p. 26), showing 
that the dip of the contact is bringing the latter nearer the vein. On level 5 the 
lode enters the breccia about 300 feet north of the shaft; but about 675 feet north 
of the shaft, near the crossing of the Emerson lode, the granite reappears and 
continues to form the west wall of the Independence lode into the Portland ground. 
Below level 5, there is practically no breccia west of the Independence lode, the 
latter being either wholly in granite or following in a general way the steep granite- 
breccia contact (fig. 62). This statement, however, requires some qualification 
with reference to the 1,400-foot level. The granite-breccia contact near the north 
end of this level is indistinct, and the narrow fissure, supposed to be the Independence 
vein, apparently enters a granitic phase of the breccia about 100 feet south of the 
Portland line. Whether or not this is merely a level irregularity in the contact 
could not be determined. 
The granite-breccia contact is hardly so well exposed in the Independence 
workings as in the Portland. In general it is fairly distinct on the upper levels, 
the granite as a rule not showing much brecciation in its vicinity. In detail it is 
