190 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
4. BUTTE COUNTY. 
Rocks from this county are also to be found under the heading* oi 
the Lassen Peak region. The following rocks were collected by H. W. 
Turner, to whom the petrographic data are due. Analyses, with twc 
exceptions, by W. F. Hillebrand, record Nos. 1432, 1456, 1461, and 
1548. Analysis G is by H. N. Stokes, record No. 1562. 
A. Granodiorite, north side of south fork of Feather River, oppo- 
site Enterprise. Described in 14th Ann., p. 441. Contains plagio- I 
clase, potash feldspar, quartz, hornblende, brown mica, and accessory 
minerals. The ferromagnesian minerals are largely altered to chlo- 
rite. P. R. C. 720. 
B. Granodiorite, 2 miles east of Bangor. Composition like A. The 
mica is largely altered to chlorite. See 14th Ann., p. 441. P. R. C. 717. 
C. Diorite, South Honcut Creek. Description supplied by Turner. 
Contains feldspar, probably all plagioclase, brown hornblende, and a 
little chlorite. P. R. C. 775. 
D. Quartz-diorite, 4.6 miles south of Table Mountain, on ridge 
between Butte and Plumas counties. Described in 17th Ann., Part I, 
p. 521. Contains hornblende, feldspar, quartz, rutile, and a little 
secondary chlorite and epidote. P. R. C. 758. 
E. Amphibole separated from E. Analysis by William Valentine, 
record No. 1723. Cr 2 3 determination by Hillebrand. 
Si0 2 . 
A1 2 3 . 
Fe 2 3 
FeO.. 
MgO . 
CaO . 
Na 2 0. 
H 2 Oatl00° 
H 2 above 100°. 
Ti0 2 
PA 
Cr 2 3 
NiO . 
MnO. 
SrO.. 
BaO.. 
Li 2 . 
A. 
70.36 
15.47 
.98 
1.17 
.87 
3.18 
4.91 
1.71 
.06 
1.00 
.20 
.11 
trace 
trace 
.06 
trace 
100. 08 
B. 
63.43 
14.20 
1.54 
4.56 
2.35 
5.51 
3.49 
2.19 
.15 
1.50 
.73 
.11 
.03 
trace 
.06 
none 
99.85 
57.87 
16.30 
1.71 
3.86 
5.50 
5.53 
5.01 
.75 
.26 
2.40 
.53 
.27 
.08 
trace 
.05 
trace 
100. 12 
54.64 
12.06 
1.81 
5.03 
11.86 
7.74 
2.35 
1.01 
.12 
2.44 
.61 
.08 
.03 
.05 
.13 
trace 
.05 
trace 
100. 01 
50.08 
7.97 
2.69 
6.71 
16.31 
11.21 
1.22 
.46 
1.40 
.76 
trace 
.16 
.49 
none 
100. 46 
