172 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [no. 223. 
4. BUFFALO PEAKS. 
Hypersthene-andesite, described by Cross in Bull 1. Contains hy- 
persthene, augite, plagioclase, magnetite, and apatite. Sp. gr., 2.742, 
16°. Analyses made by W. F. Hillebrand in the Denver laboratory. 
A. Hypersthene-andesite. Andose. P. R. C. 86 and 588. 
B, C, D. Hypersthene separated from the rock. Sp. gr., of D, 
3.307, 23°. In B and C alkalies were not tested for. In C and I) all 
the iron is given as FeO. • 
A. 
B. 
c. 
D. 
Si0 2 
56.19 
16.12 
4.92 
4.43 
4.60 
7.00 
2.96 
2.37 
1.03 
.27 
trace 
trace 
trace 
.02 
51.70 
1.72 
.30 
18.00 
25.09 
2.87 
51.16 
2.15 
50. 04 
ALOo 
2.91 
Fe 2 3 
FeO.. 
18.36 
24.25 
3.81 
17.81 
MgO 
21.74 
CaO 
6.70 
Na 2 
.27 
K 2 
H 2 
P 2 5 
MnO 
.36 
.36 
. 12 
SrO 
BaO 
CI 
99.91 
100. 04 
100. 10 
99.59 
