112 
ANALYSES OF ROCKS, IT. S. GEOLOGICAL SURVEY 
[BULL. 168. 
D. Highly altered porphyrite?, hills 1 mile north of East Gallatin 
River, near camp No. 6. Rock contains hornblende paramorphs after 
augite in a de vitrified base, with amygdules of calcite, chloritic and 
ferruginous matter derived from porphyritic augite and olivine. The 
base is also filled with needles, which may be mica. Analysis by 
Eakins, record No. 820. P. R. C. 968. 
E. Lamprophyre, Cottonwood Creek. Contains porphyritic augite 
and olivine in an indeterminate groundmass carrying augite, iron 
oxides, and mica. Analysis by Chatard, record No. 516. P. R. C. 979. 
F. Augite-porphyry, Cottonwood Creek. Contains feldspars, augite, 
and brown mica, with iron oxides, apatite, glass, and secondary calcite 
and chlorite. Carries porphyritic plagioclase and augite. No unal- 
tered olivine visible. Sp. gr. 2.785. Analysis by Eakins, record 
No. 819. P. R. C. 965. 
D. 
E. 
F. 
Si0 2 
49.47 
12.15 
1.93 
4.07 
10.86 
9.30 
2.08 
2.42 
| 4.14 
.21 
.37 
trace 
.10 
.03 
51.65 
13.89 
2.70 
4.80 
11.56 
4.07 
2.99 
4.15 
1.30 
1.89 
.55 
.21 
.08 
.15 
.19 
.19 
52.33 
15. 09 
4.31 
4.03 
6.73 
7.06 
3.14 
3.76 
| 2. 68 
.14 
1.02 
ALO, 
Fe 2 3 
FeO 
MeO 
CaO 
Na 2 
K 2 
H 2 at 120° 
H 2 above 120° 
Ti0 2 
P 9 (\ 
Cr 9 0, 
MnO 
.09 
.07 
BaO 
SO, 
co 2 . 
3.31 
100.44 
100. 37 
100. 45 
