184 
ANALYSES OF KOCKS, U. S. GEOLOGICAL SURVEY. 
[no. 228. 
Rocks U to X, also from Silverton quadrangle, were collected by 
Whitman Cross, who supplies the petrographic data. Analyses, hith- 
erto unpublished, by W. F. Hillebrand, record Nos. 2024, 2042, 2045. 
U. Quartz-latite, ridge north of Pole Creek. Amiatose near yel- 
lowstonose. Contains phenocrysts of andesine, hornblende, and a 
little biotite, in a predominant groundmass of orthoclase, plagioclase, 
quartz, and a little augite, biotite, and magnetite. P. R. C. 1353. 
V. Quartz-latite, bench south of Greenhalgh Mountain. Toscanose. 
Contains phenocrysts of oligoclase-andesine and biotite in a ground- 
mass of orthoclase, quartz, and rare accessories. P. R. C. 1354. 
W. Pyroxene-andesite, ridge west from Edith Mountain. Tonal- 
ose. Contains phenocrysts of labradorite, augite, hypersthene, bio- 
tite, and magnetite, in a groundmass which is largely glass, with 
feldspar microlites and ferritic particles. P. R. C. 1355. 
X. Pyroxene-andesite, Dolly Varden mine, Henson Creek. Ilarz- 
ose. Contains phenocrysts of labradorite, hypersthene, augite, and 
magnetite, in a groundmass of plagioclase, orthoclase, quartz, augite, 
magnetite, etc. P. R. C. 1356. 
Si0 2 . 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 Oatl05°... 
H 2 above 105 c 
Ti0 2 
Zr0 2 
P,0 R 
MnO 
BaO. 
SrO. 
Li 2 
S.... 
FeS.,. 
u. 
62. 09 
16.77 
3.96 
.99 
1.63 
4.26 
3.77 
3.68 
.50 
1.32 
.73 
trace 
.25 
.14 
.10 
.05 
trace 
none 
100. 24 
64. 93 
16. 79 
3. 54 
.32 
.65 
2.11 
3.33 
4.76 
1.12 
1.65 
.53 
.03 
.17 
trace 
.15 
trace 
trace 
trace? 
100. 08 
58. 88 
15. 93 
3.12 
2.94 
2. 30 
6. 05 
3.17 
1.86 
1.66 
2.48 
.73 
.02 
.34 
.16 
.12 
.14 
trace 
99.9^ 
56. 03 
15.97 
4.78 
3.00 
3.36 
6.44 
2.85 
3.29 
1.31 
1.08 
1.01 
trace? 
.48 
.16 
.08 
.04 
none 
99.88 
C0 2 absent. CI, F, not looked for. 
