134 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[no. 228. 
M. Bluebird granite, Nettie mine. Alaskose. An aplite. Contains 
ortkoclase and quartz, with a little plagioclase and a sprinkling of 
biotite. Analysis by H. N. Stokes, record No. 1686. 
N. Same rock and locality as M. Analysis by W. F. Hillebrand, 
record No. 1692. 
O. Pitchstone, or rhyolite-dacite obsidian, Butte. Zassenose. 
Phenccrysts of andesine, quartz, and orthoclase in a glass} r base. 
P. Rhyolite, Hyde Park dike. Tehamose. Contains sanidine, 
quartz, plagioclase, and biotite in a groundmass of quartz and feldspar. 
Analyses O, P, by Stokes, record No. 1686. 
Q. Quartz- porphyry, Modoc mine. Toscanose. Contains quartz, 
orthoclase, and plagioclase in a groundmass of quartz and feldspar. 
A few small biotites are present. Feldspar partly altered to sericite. 
Analysis by Hillebrand, record No. 1692. 
R. Altered rhyolite-porphyry, 1,800-foot level, Anaconda mine. 
Contains quartz phenocrysts, with sericite, pyrite, etc. Analysis by 
Hillebrand, record No. 1971, partial only. 
Si0 2 
AlA 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 OatllO°... 
H 2 above 110 c 
Ti0 2 
ZrO, 
co 2 
PA 
s 
so,..., 
FeS 2 
CI 
MnO 
SrO 
BaO 
Li 2 
Cu 
M. 
76. 87 
12.52 
.67 
none 
.09 
.49 
2.47 
5.78 
.25 
.52 
.11 
.05 
trace 
none 
trace 
none 
none 
trace 
99. 82 
77.05 
12.84 
. 56 
.14 
trace 
.57 
2.81 
5.52 
.22 
.48 
.12 
none 
none 
none 
trace 
100. 31 
O. 
67.55 
15.68 
.98 
1.02 
1.11 
2.51 
4.15 
2.86 
.38 
2.76 
.34 
none 
none 
.12 
.05 
trace 
.03 
.11 
none 
99.65 
74.34 
12.97 
.75 
.54 
.86 
.85 
2.49 
4.72 
1.03 
1.11 
.18 
.05 
none 
.07 
.03 
none 
trace 
trace 
.07 
trace 
100. 06 
Q. 
69.95 
15. 14 
.38 
.83 
.56 
1.45 
2.70 
6.36 
.40 
.91 
.24 
.02 
.37 
.10 
«. 39 
undet. 
.08 
.02 
.13 
trace 
.03 
100. 06 
71.01 
14.37 
.18 
.26 
.58 
.10 
1.56 
4.53 
24 
4.37 
trace? 
97.20 
"Other sulphides than pyrite are present. 
