CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
251 
15. MISCELLANEOUS ROCKS. 
A. Rhyolitic obsidian, Medicine Lake, Modoc County. Toscanose. 
Collected by J. 8. Diller, who reports it to be a banded obsidian, con- 
taining- a few minute feldspar crystals. The banding- is due to a mul- 
titude of trichites. Analysis by L. G. Eakins, record No. 1072. 
B. Tuff from Hyampom, south fork of Trinity River, Trinity County. 
Almost wholly made up of particles of clear glass. Collected and 
described by Diller. Analysis by George Steiger, record No. 1427. 
C. Tuff from Redding Creek Basin, Trinity County. Collected by 
J. S. Diller. Analysis by E. T. Allen, record No. 2020. 
D. Diabase-porphyrite, one-half mile west of Browns Valley, Yuba 
County. Auvergnose. Collected and described by W. Lindgren. 
Contains augite, plagioclase, magnetite, chlorite, and epidote. Anal- 
ysis by W. F. Hillebrand, record No. 1119. 
E. Amphibolitic schist, 1 mile northeast of Browns Valley, Yuba 
County. Collected and described by W. Lindgren. From metamor- 
phosis of C. Contains chiefly green hornblende and feldspar. Anal- 
ysis by Hillebrand, No. 1419. 
A. 
B. 
c. 
D. 
E. 
Si0 2 
73.51 
14.42 
.46 
1.49 
.33 
1.26 
4.03 
4.29 
} .04 
70.40 
13. 50 
1.31 
1.61 
.37 
.56 
2.11 
2.39 
1.05 
7.41 
60. 23 
18.64 
3.81 
.88 
1.64 
6.04 
3.87 
1.46 
.95 
1.97 
.57 
.01 
.20 
trace 
.05 
.11 
48.26 
14.83 
3.27 
5.97 
8.77 
11.38 
1.57 
1.13 
.10 
3.37 
.51 
54.13 
A1 2 3 
14.53 
Fe 2 3 
1.50 
FeO 
5.25 
MgO 
10.93 
CaO 
4.91 
Na 2 
3.53 
K 2 
.32 
H 2 at 100° 
.20 
H 2 above 100° 
4.01 
Ti0 2 
.46 
Zr0 2 
P 2 5 
.40 
trace 
.08 
trace 
.25 
.15 
trace 
.05 
trace 
1.24 
.09 
MnO 
.15 
SrO 
trace 
BaO 
.02 
Li 2 

none 
C0 2 
none 
trace 
Cr 2 0, 
100. 23 
100. 79 
100. 43 
100. 85 
100. 03 
