IGNEOUS AND CRYSTALLINE ROCKS. 
137 
IDAHO. 
Rocks collected by Waldemar Lindgren, who furnishes the petro- 
graphicdata. Those from Silver City and Hailey will be described in 
20th Ann., Part III. 
A. Quartz-monzonite, Idaho-Democrat mine, Hailey. Contains 
quartz, orthoclase, microcline, oligoclase, biotite, apatite, titanite, 
and magnetite. Sp. gr. 2.672, 27.5°. 
B. Same rock and locality as A, but in altered condition. Contains 
quartz, sericite, chlorite, calcite, pyrite, rutile, etc. Sp. gr. 2.472, 
29°. 
C. Gabbro, related to diorite, Croesus mine, Hailey. Contains 
labradorite, biotite, diallage, hypersthene, hornblende, quartz, titanite, 
magnetite, orthoclase, and chlorite. Sp. gr. 2.826, 28°. 
D. Same rock and locality as C, but in altered condition. Contains 
quartz, sericite, chlorite, calcite, pyrite, arsenopyrite, rutile, etc. Sp. 
gr. 2.898, 28°. 
Analyses A to D by W. F. Hillebrand, record No. 1826. The metals 
which are bracketed with sulphur represent sulphides. Traces of 
lithia are present in all four. 
A. 
B. 
c. 
D. 
Si0 2 
68.42 
15.01 
.97 
1.93 
1.21 
2.60 
3.23 
4.25 
.54 
.73 
.50 
.13 
none 
.06 
.03 
.12 
.20 
.02 
71.93 
12.21 
.64 
2.99 
.58 
2.59 
.23 
3.29 
.37 
2.06 
.40 
.10 
none 
.18 
none 
trace 
1.95 
57.78 
16.28 
1.02 
4.92 
4.60 
6.65 
3.25 
2.22 
.34 
.92 
1.07 
.30 
.02 
.15 
.07 
.12 
.15 
.02 
58.01 
15.72 
.64 
3.87 
2.07 
2.15 
.10 
4.79 
.31 
2.71 
1.08 
.31 
none 
.17 
none 
trace ? 
2.86 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
1 
H 2 Oatl05° 
H 2 above 105° 
Ti0 2 
P 2 5 
CoO, NiO 
MnO 
SrO 
BaO 
C0 2 
s 
.18] 
.13 
none 
.09 
trace 
none. 
> 
1.25 
1.52 
.12 
Fe 
Co, Ni 
Zn 
Pb 
.86 
.05 
1.65 
Cu .. 
As 
99.95 
99.92 
99.88 
100. 24 
