CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
217 
15. MISCELLANEOUS ROCKS. 
A. Rhyolitic obsidian, Medicine Lake, Modoc County. Collected 
by J. S. Diller, who reports it to be a banded obsidian, containing a 
few minute feldspar crystals. The banding is due to a multitude 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. 1127. 
C. Diabase-porphyrite, one-half mile west of Browns Valley, Yuba 
County. Collected and described by W. Lindgren. Contains augite, 
plagioclase, magnetite, chlorite, and epidote. Analysis by W. F. Hil- 
lebrand, record No. 1119. 
D. 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. Analy- 
sis by Hillebrand, No. 1119. 
A. 
B. 
C. 
D. 
Si0 2 
73.51 
14.42 
.46 
1.49 
.33 
1.26 
4.03 
4.29 
\ .40 
70.40 
13.50 
1.31 
1.61 
.37 
.56 
2.11 
2.39 
1.05 
7.41 
48.26 
14.83 
3.27 
5. 97 
8.77 
11.38 
1.57 
1.13 
.10 
3.37 
.51 
.25 
.15 
trace 
.05 
trace 
1.24 
54.13 
14.53 
1.50 
5.25 
10.93 
4.91 
3.53 
.32 
.20 
4.01 
.46 
.09 
.15 
trace 
.02 
none 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 Oatl00° 
H 2 above 100° 
Ti0 2 
P 2 5 
.04 
trace 
.08 
trace 
MnO 
SrO 
BaO 
Li 2 
C0 2 
100. 23 
100. 79 
100. 85 
100. 03 
