220 
ANALYSES OF ROCKS, IT. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
OREGON. 
1. BASALT, MOUNT THIELSEN. 
Partly described by Diller in Am. Journ. Sci., 3d series, vol. 28, p. 
257. A hypersthene-basalt containing hypersthene, olivine, feldspar, 
and magnetite. In the printed paper only the analyses of the ground- 
mass and the fulgurite formed in it are given. 
A. Hypersthene-basalt. 
B. Pyroxene. 
C. D. Feldspars. 
E. Groundmass. 
F. A fulgurite, or lightning tube. 
Analyses A and F by F. W. Clarke, record Nos. 108, 105; B, C, D, 
and E by T. M. Chatard, record Nos. 135, 133, 134, 128. These analy- 
ses were made early in the history of the laboratory and are by no 
means complete. 
A. 
B. 
c. 
D. 
E. 
F. 
Si0 2 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 
Ti0 2 
55.68 
18.93 
/ 8.73 
4.86 
7.99 
2.12 
.48 
.60 
53.31 
5.99 
/ 13. 43 
21.69 
3.69 
55.48 
26.91 
^ 2.32 
2.27 
8.11 
3.14 
.72 
.66 
.39 
51.95 
28.84 
^ 2.24 
1.34 
11.42 
3.22 
.59 
.40 
trace 
55.85 
22.95 
1 4.59 
3.08 
8.41 
2.16 
2.67 
.52 
55. 04 
1 28. 99 
5.85 
7.86 
1.11 
P 2 5 
trace 
99.39 
98.11 
100. 00 
100. 00 
100. 23 
98.85 
Iron oxides not separated. Analyses B, C, D, and F made on very small quantities 
of material. C and D were analyzed by the hydrofluoric acid method, and the silica 
was determined by difference. 
