200 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [bull. 168. 
9. AMADOR COUNTY. 
Rocks collected by H. W. Turner, and analyses published in 14th 
Ann., p. 441, and 17th Ann., Part I, p. 521. Additional data supplied 
by Turner. Analyses by W. F. Hillebrand, record Nos. 1432, 1456, 
and 1597. 
A. Rhyolite, south point of Buena Vista Peak. Contains sanidine, 
quartz, and biotite in a glassy groundmass. P. R. C. 729. 
B. Quartz-monzonite, north fork of Mokelumne River. Contains 
plagioclase, microcline, quartz, abundant biotite, iron ore, sphene, 
apatite, and perhaps rutile. P. R. C. 770. 
C. Quartz-monzonite, north fork of the Mokelumne River. Like 
B. P. R. C. 765. 
D. Quartz-porphyrite-schist, 2i miles southeast of Buena Vista 
Peak. Contains porphyritic quartz and hornblende, also calcite and 
other carbonates. See 14th Ann. P. R. C. 723. 
E. Quartz-diorite-gneiss, north fork of Mokelumne River. Con- 
tains plagioclase, hornblende, quartz, brown mica, accessory biotite, 
and iron oxide. P. R. C. 764. 
F. Diorite-porphyry, north fork of Mokelumne River. Contains 
plagioclase, brown hornblende, epidote, and a little sulphide of iron 
and chlorite. P. R. C. 769. 
Si0 2 
A1 2 3 
FeA 
FeO 
MgO 
CaO 
Na 2 , 
K 2 
H 2 Oat 100°... 
H 2 above 100 : 
Ti0 2 
NiO. 
MnO 
SrO . 
BaO. 
Li 2 
C0 2 . 
FeS 2 
73.23 
12.73 
.99 
.16 
.22 
.61 
1.91 
5.17 
.53 
4.51 
.09 
.02 
trace 
none 
.02 
trace 
100. 19 
70.75 
15. 13 
.98 
1.43 
.73 
3.09 
3. 05 
3.62 
.10 
.51 
.42 
.10 
none 
trace 
.04 
.12 
trace 
none 
.06 
100.13 
C. 
70.43 
15. 51 
.96 
1.28 
.37 
2.76 
2.75 
5.14 
.08 
.40 
.24 
.11 
(?) 
trace 
.05 
.20 
trace 
none 
trace 
100. 28 
70. 29 
11. 83 
1.30 
2.08 
1.24 
2.30 
2.68 
3.05 
.10 
1.35 
.29 
.07 
.12 
trace ? 
' .07 
none 
3.25 
100.02 
57. 41 
17.71 
2.16 
5.01 
3.38 
6.73 
3.12 
1.82 
.20 
1.14 
1.04 
.24 
.02 
.15 
.04 
.09 
trace 
none 
none 
100. 26 
55.18 
17.35 
2.77 
3.90 
4.80 
7. 98 
3.42 
1.42 
.16 
1.52 
.83 
.20 
.03 
.15 
.06 
.04 
trace 
none 
.28 
100. 09 
