208 
ANALYSES OF EOCKS, IT. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
F. Amphibole-biotite granite, Nevada Falls trail, Yosemite Valley. 
Contains alkali feldspar, plagioclase, quartz, amphibole, biotite, mag- 
netite, and apatite. 
G. Biotite-granite, base of El Capitan, Yosemite Valley. Contains 
alkali feldspar, plagioclase, quartz, biotite, titanite, apatite, and iron 
oxides. 
H. Brown mica separated from G. 
Analyses F, G, and H by William Valentine, record Nos. 1732, 1733. 
1. Amphibole separated from quartz-monzonite, Tioga road, south- 
east of Mount Hoffman. Sp. gr. 3.203, 2.15°. 
J. Mica separated from the same rock as I. Sp. gr. 3.05, 21°. 
Analyses I and J by W. F. Hillebrand, record No. 1774. 
Samples G to J are described by Turner in Amer. Journ. Sci., 4th 
series, vol. 7, p. 294. 
F. 
G. 
H. 
I. 
J. 
SiO, 
66. 83 
15. 24 
2.73 
1.66 
1.63 
3.59 
3.10 
4.46 
none 
.56 
.54 
.18 
.04 
71.^08 
15.90 
.62 
1.31 
.54 
2.60 
3.54 
4.08 
none 
.30 
.22 
.10 
.08 
35. 64 
18.62 
5.54 
14.60 
9.72 
.90 
.38 
9.22 
.48 
2.54 
1.12 
.20 
47.49 
7.07 
4.88 
10. 69 
13.06 
11.92 
.75 
.49 
35. 75 
14.70 
4.65 
14. 08 
12.37 
. 17 
. 32 
9. 19 
1.03 
3.64 
3.16 
.03 
A1,0 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K.,0... 
H 2 Oat 110° 
H 2 above 110° 
Ti0 2 
1.86 
1.21 
none 
P 2 5 
Zr0 2 
v,o, 
.04 
none 
.51 
.02 
none 
none 
trace 
.05 
trace 
.45 
.02 
(?) 
.12 
Cr 2 3 
MnO 
.10 
.15 
.79 
NiO, CoO 
SrO 
.03 
.11 
trace 
trace 
.02 
.02 
.04 
trace 
trace 
.02 
BaO..... 
Li 2 ... 
co 2 . 
trace 
trace 
CL. 
F 
.26 
.06 
.17 
Less 0.-.. .... 
100. 82 
100. 60 
100. 01 
.11 
100. 05 
.02 
99.90 
.07 
99.90 
100. 03 
99.83 
