116 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
2. BUTTE AND BOULDER DISTRICTS. 
Rocks received from W. H. Weed and G. W. Tower. The granite 
rocks are described by Weed in Journ. Geol., vol. 7, p. 737. All the 
rocks will be described in the 21st Annual Report. 
A. Butte granite. A quartz-nionzonite, variety banatite, from Walk- 
erville Station. Contains quartz, andesine, orthoclase, hornblende, 
and biotite, with a little titanite, apatite, and magnetite. 
B. Biotite from A. 
C. Amphibole from A. 
D. Butte granite, like A, from the Frohner mine, 10 miles south of 
Helena. 
Analyses by H. N. Stokes, record Nos. 1686, 1787, 1808. 
Si0 2 .. 
A1 2 3 - 
Fe 2 3 . 
FeO.. 
MgO . 
CaO.. 
Na 2 0. 
K 2 0.. 
Ti0 2 . 
P 2 5 . 
MnO 
SrO. 
BaO. 
Li 2 
S0 3 . 
CI... 
F ... 
Less (X 
63.88 
15.84 
2.11 
2.59 
2.13 
3.97 
2.81 
4.23 
.22 
.66 
.65 
.21 
.07 
.02 
.09 
trace 
.34 
trace 
99.82 
B. 
35.79 
13.70 
5.22 
13.72 
12.13 
.05 
.15 
9.09 
1.21 
3.64 
3.51 
.10 
.19 
none 
.13 
trace 
.20 
.76 
99.59 
.37 
99.22 
c. 
45.73 
6.77 
4.94 
10.39 
12.32 
11.25 
.77 
1.22 
.49 
2.29 
1.43 
.35 
.54 
none 
none 
trace 
.28 
98.77 
.12 
98. 65 
D. 
64.17 
15.25 
2.16 
2.98 
2.60 
4.24 
2.62 
4.34 
.16 
.65 
.67 
.16 
.04 
trace 
.07 
trace 
.07 
trace 
100.18 
