BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 483 
them only a fraction of an inch in width, which collectively compose the pay shoot. 
The value of the ore thus lies chiefly in the screenings. 
The various smaller lodes in the breccia, such as those of the northeast zone, 
present no structural features of sufficient interest to merit detailed description. 
CHARACTER OF ORE. 
The general types of ore are found in the Ajax mine, one consisting of meta- 
somatically altered granite and the other of sheeted and veined breccia or phonolite. 
The granitic ore has been the more important and is of the same general char¬ 
acter as that found in the Portland, Strong, and Independence mines. Viewed at 
a little distance in the stope walls the ore does not appear very different from the 
unaltered granite and exhibits the usual conspicuous porphyritic structure due to 
the development of phenocrystic aggregates of pink microcline. Closer examina¬ 
tion, however, shows that in the ore all the other principal constituents of the 
granite—namely, the quartz, mica, and oligoclase—have been altered to a porous 
aggregate of adularia, quartz, fluorite, and an obscure green mineral that is prob¬ 
ably roscoelite, as the presence of vanadium is shown by chemical analysis. Pyrite 
occurs in all the secondary minerals and probably calaverite also, though this 
mineral is very difficult to distinguish from the pyrite, as it rarely occurs in large 
crystals. It is said to be sometimes visible in the ore, though none has been iden¬ 
tified with certainty in the specimens collected. The biotite of the granite is the 
first mineral to undergo alteration and is transformed to aggregates of quartz, 
fluorite roscoelite, pyrite, and calaverite. The apatite and zircon of the rock 
appear to be unaffected by the metamorphism. The granitic ore is frequently 
traversed by veinlets filled with pyrite, which so far as known is not auriferous. 
Analyses of the comparatively unaltered granite and of a partly altered specimen 
constituting ore are given below. The two specimens were taken about 1 foot apart. 
Chemical analyses of granite and ore from Ajax mine. 
I. 
II. 
I. 
II. 
66.20 
59.58 
S0 3 . 
None. 
None. 
Alj0 3 .... . 
14.33 
16.00 
Cl. 
Trace. 
(?) 
2.09 
.30 
F. 
(?) 
a.69 
FeO . 
1.93 
.65 
6.12 
c 4 .78 
MtrO . 
.89 
.03 
MnO. 
.13 
Trace. 
1.39 
2.03 
BaO. 
.18 
.11 
NajO 
2.58 
.98 
SrO. 
Trace. 
.01 
KjO . 
7. 31 
11.93 
Li 2 0. 
Trace. 
Trace. 
I1 2 0— ... 
.48 
.32 
V 2 0 3 . 
.39 
h 2 o+ . 
.83 
.81 
M 0 O 3 . 
.01 
Ti0 2 . 
.65 
.75 
Zr0 2 . 
.02 
(?) 
99.74 
99.95 
C0 2 . 
.36 
.26 
Less O lor F. 
.29 
p 2 o 5 . 
.25 
.32 
99.74 
99. 66 
a 1.42 CaF 2 . b 0.067 S. c 2.55 S. 
