230 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[NO. 228. 
7. PLACER COUNTY. 
First, a series of rocks from the Ophir mining district, described by 
Lindgren in 14th Ann., p. 249. Analyses by W. F. Hillebrand, record 
Nos. 1419, 1433, 1434. 
A. Granodiorite, quarries at Lincoln, 8 miles west of Ophir. Tonal- 
ose. Contains feldspars, quartz, biotite, and hornblende. 
B. Pyritiferous amphibolite, Conrad tunnel. Partly altered. Con- 
tains py rite, hornblende, magnetite, feldspars, quartz, epidote, chlorite, 
a few scales of mica, rutile, and carbonates. Sp. gr., 2.901, 23°. 
C. Dike rock, near camptonite, Casey's tunnel, Flat Ledge, Duncan 
Hill. Flacerose. Contains hornblende, feldspars, p} 7 rite, and apatite, 
with secondaiy epidote and quartz. 
D. Altered wall rock, Mina Rica vein. Sp. gr., 2.979, 20°. 
E. Altered wall rock, Plantz vein. These rocks, D and E, contain 
quartz, muscovite, a little chlorite, pyrite, and sphene, with carbonates 
of calcium, magnesium, and iron. 
Si0 2 
AL0 3 
Fe 2 3 
FeO 
MgO 
CaO 
NaX> 
K 2 
H 2 Oatl00°.... 
H 2 above 100° 
Ti0 2 
FA 
MnO 
Ni,Zn 
SrO 
BaO 
Li,0 
so 3 
co 2 
FeS, 
Cu 2 S(?) 
65.54 
16.52 
1.40 
2.49 
2.52 
4.88 
4.09 
1.95 
.12 
.59 
.39 
.18 
.06 
trace 
trace 
trace 
100. 73 
B. 
45.56 
14. 15 
1.20 
9.83 
6. 76 
2.30 
1.57 
1. IS 
.23 
4.84 
1.11 
.14 
.25 
traces 
trace 
trace 
trace 
.03 
3.04 
7.86 
.10 
100. 15 
60. 09 
16.43 
2.28 
3.01 
4.37 
5.76 
4.52 
.70 
.20 
1.16 
.63 
.12 
.12 
trace 
trace 
none 
trace 
.07 
.34 
99.80 
37. 01 
12.99 
.43 
3.57 
5.49 
9.78 
.13 
4.02 
.13 
1.92 
.85 
.06 
.24 
traces 
trace 
trace 
trace 
.04 
15. 04 
7.99 
99.69 
46.13 
15. 82 
.89 
2.27 
2.13 
10.68 
.17 
5. 30 
.12 
2.42 
.67 
.10 
.09 
traces 
trace 
trace 
trace 
.04 
11.24 
1.61 
'.»«». 
