CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
127 
MONTANA. 
1. MADISON AND GALLATIN VALLEYS. 
Rocks collected by A. C. Peale and G. P. Merrill. Described by 
Merrill in Proc. U. S. National Museum, vol. 17, p. 637. Sec also 
Bull. 110, p. 17. 
A. Basalt?, east side of Bozeman Creek, 2^ miles southeast of Boze- 
man. Kentallenose. Contains olivine and augite, chloritized and 
serpentinized. The colorless groundmass contains apparently two 
feldspars and a pyroxene, with grains of iron oxide. Analysis by T. 
M. Chatard, record No. 517. Sp. gr., 2.86. P. R. C. 971. 
B. Pyroxene from A. Analysis by L. G. Eakins, record No. 1046. 
C. Portion of A soluble in hydrochloric acid. Contains olivine, iron 
oxides, and decomposition products. Analysis by Eakins, record 
No. 817. 
Si0 2 
A1 2 3 
FeA 
FeO 
MgO 
CaO 
Na 2 
K 2 () 
H 2 Oatl20° 
H 2 above 120° 
Ti0 2 
PA 
oa 
MnO 
46.90 
10. 17 
1.22 
5.17 
20.98 
6.20 
1.16 
2.04 
1.04 
4.38 
.41 
.44 
.33 
.10 
100. 54 
B. 
52. 50 
2.26 
2.05 
2.47 
17.11 
21.70 
.35 
.07 
.64 
1.07 
trace 
100. 32 
c. 
20. 88 
3. 89 
2.21 
4.28 
16.44 
1.01 
trace 
trace 
trace 
48.71 
