156 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[no. 228. 
IDAHO. 
Rocks A to K, inclusive, are described by Waldemar Lindgren in 
20th Ann., Part III, p. 75. 
A. Quartz-monzonite, Idaho-Democrat mine, Hailey. Toscanose. 
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. Diorite, Croesus mine, Haile3 r . Andose. Contains labradorite, 
biotite, diallage, l^persthene, 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. 
Si0 2 . 
ALO, 
A. 
FeO 
MgO 
CaO '..... 
Na 2 
K 2 
H 2 Oat 105°.... 
H 2 above 105° 
Ti0 2 ---- 
PA 
CoO, NiO 
MnO 
SrO 
BaO 
co 2 
s 
Fe 
Co, Ni 
Zn 
Pb 
Cu 
As 
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 
99. 95 
i'.. 
71.93 
12.21 
.64 
2. 99 
.58 
2.59 
.23 
3.29 
.37 
2.06 
.40 
.10 
none 
.18 
none 
trace 
1.05 
.18 
.13 
none 
.09 
trace 
none 
99.92 
C. 
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 
99.88 
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 
1.25 
1.52 
.12 
.86 
.05 
1.65 
100. 24 
