206 
ANALYSES OF ROOKS, U. S. GEOLOGICAL SURVEY, 
[BULL. 168. 
J. Amphibole-gabbro, Beaver Creek, Big Trees quadrangle. Con- 
tains labradorite and amphibole, with a little pyrite and pyrrhotite. 
Analysis by H. N. Stokes, record No. 1752. 
K. Amphibole separated from J. Analysis by William Valentine, 
record No. 1733. 
L. Olivine-gabbro, just east of south end of Phoenix reservoir. 
Contains plagioclase, a few grains of alkali feldspar, augite, rhombic 
pyroxene, amphibole, olivine, magnetite, and iron sulphide, with a 
little secondary chlorite and epidote. Analysis by H. N. Stokes, 
record No. 1750. 
For description of J and K see Turner, Amer. Jour. Sci., -1th series, 
vol. 7. p. 294. The description of L is hitherto unpublished. 
J. 
K. 
L. 
Si0 2 
47.27 
20.82 
1.85 
4.26 
6.44 
13.02 
2.75 
.22 
.08 
1.27 
.92 
.74 
.02 
trace 
trace 
trace 
none 
46.08 
10.52 
2.81 
8.30 
14.40 
12.64 
1.62 
.34 
.17 
1.97 
.77 
.18 
.04 
43.41 
23.15 
3.72 
4.39 
7.65 
14.27 
.82 
.22 
.18 
1.53 
.39 
.02 
A1 2 3 
Fe 2 O s 
FeO • 
MgO 
CaO 
Na 2 
K 2 . . 
H 2 at 1 10° . 
H 2 above 110° 
Ti0 2 
P 9 0. 
V 9 0, 
Cr 9 0o 
none 
.08 
MnO 
.15 
SrO 
Li 2 
none 
trace 
.10 
.14 
trace 
co 2 
FeS 2 
CI 
.20 
trace 
99.86 
99.99 
100. 07 
