CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
227 
6. NEVADA CITY AND GRASS YALLEY. 
Rocks of a mining district in Nevada County, described by Lind- 
gren in 17th Ann., Part II, p. 1. 
A. Granodiorite, 1 mile southeast of Nevada City. Yellowsto?iose. 
Contains hornblende, biotite, quartz, plagioclase, orthoclase, magnet- 
ite, apatite, sphene, and pyrite. Analysis by W. F. Hillebrand, 
record No. 1478. 
B. Granodiorite, Kate Hayes Hill, Grass Valley. Harzose. Con- 
tains plagioclase, orthoclase, quartz, hornblende, pyrite, magnetite, 
apatite, sphene, and zircon. Analysis by Hillebrand, No. 1478. 
C. Hornblende-porphyrite, Nevada City. Tonalose. Contains feld- 
spar, hornblende, quartz, epidote, sericite, and biotite. Analysis b} T 
H. N. Stokes, record No. 1531. 
D. Quartz-porphyrite, New Ophir claim, Grass Valley. Tonalose. 
Contains plagioclase, quartz, uralite, epidote, and augite, and horn- 
blende altered into chlorite. Analysis by Stokes, No. 1531. 
E. Diabase, near Maryland mine, Grass Valley. Ornose. Contains 
feldspar, augite, hornblende, ilmenite, pyrrhotite, p} 7 rite, and some 
chlorite. Analysis by Stokes, No. 1522. 
F. Diabase, Grass Valley. Bandose. Contains feldspar, pyroxene, 
hornblende, ilmenite, pyrrhotite, pyrite, and chlorite, and probably a 
little quartz. Analysis by Stokes, No. 1522. 
Si0 2 
AiA 
FeA 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 OatllO°..._ 
H 2 () above 110° 
Ti0 2 
PA 
CrA 
MnO 
SrO 
BaO 
Li 2 
S0 3 
FeS 2 
CuS (?) 
66. 65 
16.15 
1.52 
2.36 
1.74 
4.53 
3.40 
2.65 
.18 
.72 
.38 
.10 
.10 
trace 
.07 
trace 
.02 
100.57 
B. 
63.85 
15.84 
1.91 
2.75 
2.07 
4.76 
3.29 
3.08 
.28 
1.65 
.58 
.13 
c. 
62.09 
16.69 
1.45 
3.76 
1.93 
6.08 
3.36 
1.84 
.19 
1.47 
.32 
.39 
.07 
trace 
.06 
trace 
.04 
100. 36 
trace 
D. 
.10 
63. 39 
16.58 
1.41 
3.08 
2.15 
4.76 
3. 47 
2.79 
.22 
1.87 
.44 
.14 
trace 
51.01 
11. 89 
1.57 
6.08 
8.87 
10.36 
4.17 
.15 
.24 
2.09 
.98 
.17 
.04 
trace 
10 .11 
1.73 
trace 
99. 77 100. 41 
99.35 
53.19 
17.12 
4.35 
5.16 
3.98 
9.39 
2.79 
.28 
.17 
1.21 
1.34 
.13 
none 
trace 
trace 
.94 
100. 05 
