CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
135 
3. BOULDER BATHOLITH. 
Rocks collected bj r W. H. Weed, who supplies the petrographic 
data. 
A. Quartz-monzonite, or "Butte granite," from the Frohner mine, 
10 miles south of Helena, Harzose. Contains quartz, andesine, ortho- 
clase, hornblende, and biotite, with minor accessories. 
B. Granite, Boulder type, near Boulder. Near adamellite. Tos- 
canose. Contains quartz, feldspar, black mica, and dark-green horn- 
blende. Has an unusual amount of plagioclase. 
C. Diorite, Red Mountain. Andose. Contains pale-green to color- 
less hornblende, plagioclase varying from labradorite to albite, some 
orthoclase, and a little quartz. Biotite, apatite, and magnetite also 
occur. 
D. Diorite, Red Mountain. Kentallenose. Contact of granite with 
limestones. Consists mainly of green hornblende and "basic" plagio- 
clase. Little quartz present. 
E. Quartz-monzonite, Red Rock Creek. Harzose. Contains horn- 
blende, augite, biotite, plagioclase, and orthoclase, with a little mag- 
netite and apatite. 
Analyses by H. N. Stokes, record Nos. 1686, 1787. 
Si0 2 
A1 2 3 
FeA 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 0atll0°. 
Ti0 2 ., 
P 2 5 .. 
Cr 2 3 . 
MnO. 
SrO.. 
BaO.. 
Li 2 . 
so 3 
CI. 
A. 
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 
i'.. 
67.12 
15. 00 
1.62 
2.23 
1.74 
3.43 
2.76 
4.52 
.09 
.58 
.48 
.15 
none 
.06 
.03 
.07 
trace 
trace 
99.88 
56. 41 
17.62 
1.24 
3. 55 
3.97 
8.66 
3.25 
2.61 
.14 
.76 
.68 
.49 
.08. 
.08 
.09 
none 
none 
none 
.07 
99.70 
49.22 
12.02 
2.77 
8.80 
9.29 
10. 56 
1. 90 
1.70 
.27 
1.63 
.95 
.43 
trace 
.03 
.03 
trace 
.05 
.04 
.08 
99.77 
E. 
61.64 
15.63 
3.39 
2.69 
2.82 
4.90 
2.64 
3. 72 
.28 
.91 
.71 
.21 
trace 
.04 
.04 
.08 
trace 
99.70 
