246 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[NO. 228. 
E. Andesitic obsidian, Clear Lake. Li/parose. Shows grains of 
plagioclase, augite, and hypersthene. Sp. gr., 2.391. 
F. Andesite(asperite), Clear Lake. Yellowstonose. Contains pyrox- 
ene, plagioclase, magnetite, and sometimes biotite. Pyroxene mostly 
rhombic. Sp. gr., 2.664. 
G. Obsidian, south of Borax Lake. Varingose. Sp. gr., 2.390. 
H. Basalt, south of Burns Valley. Andose. Rich in olivine, with 
a microlitic groundmass of plagioclase and augite. Sp. gr., 2.380. 
I. Ordinary basalt, Knoxville. 
E. 
F. 
G. 
H. 
*■ 
SiOo 
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 
} - 
57. 37 
15.66 
2.06 
4.46 
8.84 
4.94 
3. 05 
1.51 
.61 
.12 
.60 
.02 
} 
} 
51.66 
ALOo 
11.22 
Fe 2 3 
FeO 
1.42 
.48 
.99 
5.34 
4.65 
7.62 
MgO . 
13. 61 
CaO 
7.72 
Na 2 
5.98 
K 2 
.89 
H 2 at 100° 
H 2 above 100° 
.29 
.24 
.01 
1.06 
Ti0 2 
trace 
P„0, 
O 2 3 
.25 
MnO 
trace 
.70 
.20 
.12 
.12 
.27 
.41 
.12 
NiO 
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. 
Si0 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 3 
MnO 
NiO 
.04 
100.03 
100. 38 
99. 93 
