164 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
10. MISCELLANEOUS ROCKS. 
A. Rhyolite, east bank of Arkansas River, Nathrop. Described by 
Cross in Proc. Colorado Sci. Soc., vol. 2, p. 69. Contains quartz and 
sanidine in a groundmass mainly of quartz and alkali feldspar. This 
rock carries topaz and spessartite in its lithophysae. Analysis made 
by L. G. Eakins in the Denver laboratory. Sp. gr. 2.602, 29°. 
B. Granite, Platte Canyon. Described by E. B. Mathews in Bull. 
150, p. 172. Contains microcline, quartz, biotite, oligoclase, and nuor- 
ite. Apatite, zircon, magnetite, hematite, limonite, epidote, and 
rutile (?) are sometimes present. Analysis by H. N. Stokes, record 
No. 1314. 
C. Hornblende-porphyrite, Hermano Peak, Sierra El Late. De- 
scribed by Cross in 14th Ann., p. 165. Contains plagioclase, horn- 
blende, rare quartz, and a little biotite. Analysis by W. F. Hillebrand, 
record No. 1429. 
D. Hornblende-porphyrite, Ute Peak, Sierra El Late. Described 
by Cross in 14th Ann., p. 165. Contains plagioclase, hornblende, and 
very little augite, in a groundmass of quartz, orthoclase, and plagio- 
clase. Analysis by Hillebrand, No. 1429. 
E. Porphyritic augite-diorite, Lone Cone, San Miguel Mountains. 
Described by Cross in 14th Ann., p. 165. Contains plagioclase, augite, 
hornblende, and biotite, in a groundmass of quartz, orthoclase, and 
plagioclase. Inclusions of magnetite and apatite in the augite. Analy- 
sis by Hillebrand, No. 1429. 
A. 
B. 
C. 
D. 
E. 
Si0 2 
69.89 
17.94 
.39 
.52 
.14 
trace 
4.21 
4.38 
} 2.07 
77.02 
11.63 
.32 
1.09 
.14 
1.24 
2.85 
5.21 
} ■'« 
62.65 
16.68 
2.35 
2.63 
1.43 
4.96 
4.45 
2.75 
.27 
.66 
.42 
.28 
.16 
.11 
.13 
trace 
59. 42 
16.79 
3.23 
3.29 
2.24 
5.57 
4.15 
2.' 82 
.27 
.79 
.68 
.35 
.13 
.07 
.14 
trace 
.44 
59.19 
18.00 
3.07 
2.32 
1.41 
6.55 
4.01 
2.74 
.46 
1. 06 
.58 
.29 
.19 
.13 
.18 
trace 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 OatlOO° 
H 2 above 100° 
Ti0 2 
P 2 0, 
trace 
.23 
MnO 
trace 
SrO 
BaO 
Li 2 
trace 
CO a 
99.77 
99. 85 
99.93 
100. 38 
100. 18 
