104 ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
5. MISCELLANEOUS ROCKS. FIRST GROUP. 
[BUl.L. 168. 
Collected and investigated by Arnold Hague and J. P. Iddings. 
A. Black obsidian, Obsidian Cliff. Described by Iddings, 7th Ann. 
Contains microlites of augite and magnetite, with traces of quartz#ind 
feldspar. Analysis by J. E. Whitfield, record No. 224. 
B. Red obsidian, Obsidian Cliff. Described by Iddings, 7th Ann. 
Like A, with ferric oxide replacing magnetite. Analysis by Whit- 
field, No. 223. 
C. Obsidian, east of Willow Park. Black and opaque. Described 
by Iddings, Bull. Phil. Soc. Washington, vol. 12, p. 204. Analysis by 
Whitfield, No. 222. 
D. Lithoidite, Obsidian Cliff. Described by Iddings, Bull. 150, 
p. 153. Contains quartz and sanidine, with a little magnetite and 
augite. Analysis by Whitfield, No. 425. 
E. Rhyolite, Upper Geyser Basin. See Iddings, Bull. Phil. Soc. 
Washington, vol. 12, p. 204. Analysis by F. A. Gooch, record No. 
114. 
F. Rhyolite, Tower Creek. See Iddings, Bull. Phil. Soc. Washing- 
ton, vol. 12, p. 204. Analysis by Gooch, No. 115. 
A. 
B. 
c. 
D. 
E. 
F. 
Si0 2 
AiA 
Fe 2 3 ---- 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 
Ti0 2 
PA 
MnO 
Li 2 
74.70 
13.72 
1.01 
.62 
.14 
.78 
3.00 
4.02 
.62 
none 
none 
trace 
75.52 
14.11 
1.74 
.08 
.10 
.78 
3.92 
3.63 
.39 
none 
72.59 
13.47 
1.58 
1.32 
1.05 
2.12 
4.63 
2.52 
.18 
.52 
75.50 
13.25 
1.02 
.91 
.07 
.90 
4.76 
2.85 
.41 
none 
none 
none 
.06 
.32 
70.92 
13.24 
3.54 
.66 
.23 
1.42 
4.28 
4.25 
.57 
.16 
.18 
.14 
none 
71.85 
13.17 
2.17 
1.34 
.63 
2.25 
4.06 
3.89 
.43 
.43 
.14 
.12 
none 
none 
SO, 
FeS 2 
.40 
.11 
.26 
99.91 
100. 38 
100. 24 
100.05 
100.59 
100.48 
