206 
ANALYSES OF BOCKS, IT. S. GEOLOGICAL SURVEY. 
[NO. 228. 
The following- rocky, G to X, inclusive, were collected by J. E. 
Spurr, who furnishes the petrographic data. Unpublished hitherto, 
except when otherwise stated. 
G. Olivine-basalt, Crater, Silver Peak. Hessose. Analysis by 
George Steiger, record No. 1883. Contains plagioclase, olivine, and 
magnetite, in a groundmass of feldspar and olivine. 
H. Homblende-pyroxene-biotite-quartz-latite, Coyote Springs, north 
end of Pah-Ute Range. Harzose. Analysis by W. F. Hillebrand, 
record No. 1881. Phenocrysts of hornblende, biotite, plagioclase, 
quartz, and magnetite, in a brown, glassy groundmass. 
I. Biotite-quartz-monzonite, Cherry Creek, Egan Range. Amiatose. 
Analysis by H. W. Stokes, record No. 1882. Contains quartz, biotite, 
and plagioclase. 
J. Quartz-muscovite rock, Belmont. Described by Spurr in Amer. 
Journ. Sci., 1th ser., vol. 10, p. 358. Analysis by Stokes, No. 1882. 
Contains quartz and muscovite, with some calcite and orthoclase, and a 
little zircon. P. R. C. 1272. 
K. Hornblende-quartz-andesite, Mason's Butte, Walker River Valley. 
Andose. Described by Spurr, Journ. Geol., vol. 9, p. 593. Analysis by 
Stokes, record No. 1882. Phenocrysts of feldspar, pale-green horn- 
blende (partly altered to calcite, chlorite, and epidote), and quartz, in 
a groundmass of feldspar and hornblende, with quartz, pyrite, and 
siderite. 
L. Hornblende-biotite-quartz diorite, Mason's Butte. Tonalose. 
Described by Spurr, as under K. Analysis t:ry Stokes, No. 1882. 
Contains oligoclase, quartz, hornblende, and biotite. 
U. 
H. 
I. 
J. 
K. 
L. 
Si0 2 
ALA 
47.09 
18.40 
2.66 
5.62 
7.06 
10.19 
2.37 
1.34 
.66 
2.37 
1.19 
62.97 
15.52 
4.03 
1.45 
2.07 
5.31 
3.31 
3.46 
.66 
.48 
.67 
trace 
.18 
.18 
trace 
undet. 
.10 
.02 
.09 
trace 
67.60 
15.89 
1.77 
1.82 
.96 
3.38 
3.39 
3.39 
.23 
.87 
.60 
84.15 
9.67 
.51 
.07 
.04 
.53 
2.65 
1.57 
.21 
.74 
trace 
53.37 
16.57 
3.84 
2.45 
5.79 
6.30 
3.40 
2.55 
.39 
2.23 
.86 
60. 25 
17.90 
Fe 2 3 
3.08 
FeO 
2.44 
MgO 
2.44 
CaO 
5.57 
Na 2 
4.29 
K 2 
1.89 
H 2 Oat 105° 
.20 
H 2 above 105° 
Ti0 2 
1.24 
.65 
Zr0 2 
co 2 
none 
.54 
.03 
none 
.19 
none 
trace 
1.61 
.29 
none 
P.A 
.25 
S.. 
F 
trace 
trace 
undet. 
.02 
trace 
trace 
undet. 
MnO 
none 
undet. 
.17 
.08 
trace 
undet. 
.06 
SrO 
.07 
BaO 
undet. 
Li 2 
99.69 
100. 50 
100. 09 
100. 16 
99. 73 
100.33 
