212 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
E. Andesitic obsidian, Clear Lake. Shows grains of plagioclase, 
augite, and hypersthene. Sp. gr. 2.391. 
F. Andesite (asperite), Clear Lake. Contains pyroxene, plagioclase, 
magnetite, and sometimes biotite. Pyroxene mostly rhombic. Sp. gr. 
2.664. 
Gr. Obsidian, south of Borax Lake. Sp. gr. 2.390. 
H. Basalt, south of Burns Valley. Rich in olivine, with a microlitic 
groundmass of plagioclase and augite. Sp. gr. 2.380. 
I. Ordinary basalt, Knoxville. 
E. 
F. 
G. 
H. 
I. 
SiO, 
74.01 
12. 95 
65.43 
17.10 
2.39 
1.19 
1.48 
3.88 
3.66 
2.83 
.20 
.36 
.83 
trace 
75.40 
7.72 
1.41 
1.26 
1.55 
8.09 
4.52 
} ,s 
57.37 
15.66 
51. 66 
11.22 
7.62 
13.61 
7.72 
5.98 
.89 
1.06 
trace 
A1 2 3 
Fe.,Oo .. 
2. 06 L 
4.46 1 
FeO 
1.42 
.48 
.99 
5.34 
4.65 
MgO 
8.84 
4.94 
3.05 
1.51 
.61 
.12 
.60 
.02 
} 
CaO 
Na 2 
K 2 
H 2 at 100° 
H 2 above 100° 
Ti0 2 
.29 
.24 
.01 
P 9 s 
Cr 2 3 
.25 
.12 
MnO 
trace 
.70 
.20 
.12 
.27 
.41 
NiO 
CI 
.07 
.12 
100. 45 
100. 25 
100. 62 
99.92 
100. 13 
J. Light-green, marmolitic serpentine, New Idria. 
K. Black serpentine, Sulphur Bank. 
L. Light-green serpentine, Sulphur Bank. 
J. 
K. 
L. 
Ri0 2 - 
41.54 
2.48 
1.37 
40.42 
14.18 
39.64 
1.30 
7.76 
37. 13 
13.81 
.29 
.12 
• 
.33 
41.86 
.69 
4.15 
38.63 
14.16 
.24 
.20 
trace 
A1 2 3 
FeO 
MgO 
H 2 
Cr 2 O s 
MnO 
NiO 
.04 
100. 03 
100. 38 
99.93 
