CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
Ill 
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. See also 
Bull. 110, p. 47. 
A. Basalt?, east side of Bozeman Creek, 2£ miles southeast of Boze- 
man. Contains olivine and augite, chloritized and serpentinized. The 
colorless groundmass contains apparently two feldspars and a pyrox- 
ene, 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 
A1A 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 at 120° . . . 
H 2 above 120 
Ti0 2 
P 2 5 
Cr 2 3 
MnO 
A. 
46. 90 
10.17 
1.22 
5.17 
20.98 
6.20 
1.16 
2.04 
1.04 
4.38 
.41 
.44 
.33 
.10 
B. 
100. 54 
52. 50 
2.26 
2.05 
2.47 
17.11 
21.70 
.35 
.07 
.64 
1.07 
trace 
100. 32 
20.88 
3.89 
2.21 
4.28 
16.44 
1.01 
trace 
trace 
trace i 
48.71 
