226 
ANALYSES OF KOOKS, U. S. GEOLOGICAL SUKVEY. [no. 228. 
F. Diabase-porphyry, dike east of Milton. Camptonose. Contains 
labradorite and other plagioclase, augite, and hornblende, the last 
mineral being perhaps secondary. P. R. C. 733. 
G. Hypersthene-andesite, point northeast of Goody ears Bar. Yel- 
lowstonose. Contains plagioclase and rhombic pyroxene, a little 
augite, and scales which seem to represent former biotite, now replaced 
by magnetite. P. R. C. 731. 
H. Hornblende- pyroxene-andesite, dike southeast of Poker Flat. 
Tonalose. Contains plagioclase, augite, hornblende, magnetite, some 
glass, and occasional quartz. P. R. C. 736. 
I. Quartz-bearing andesite, northwest of Downieville. Tonalose. 
Contains plagioclase, augite, enstatite, magnetite, occasional quartz, 
and probably glass. P. R. C. 753. 
F. 
G. 
H. 
I. 
Si0 2 
51.27 
66.94 
59.34 
60.02 
ALA 
12.14 
16. 49 
17.61 
16. 07 
Fe 2 3 
2.51 
1.41 
3.63 
2. 17 
FeO 
6.71 
1.87 
2.28 
3.46 
MgO 
10.88 
1.98 
3. 50 
4.57 
CaO 
10.32 
2.00 
4.77 
3.88 
6.45 
3.40 
7.01 
Na 2 
3.55 
K 2 
1.63 
1.65 
1.94 
1.59 
H.,0 at 100° 
.17 
1.16 
.35 
22 
.64 
.74 
.24 
.45 
H 2 above 100° 
TiO, 
.60 
.21 
.30 
12 
.32 
.25 
.42 
17 
P 2 5 
Cr 2 3 
trace 
NiO 
.04 
.21 
trace? 
MnO 
.13 
.05 
.12 
.04 
.10 
trace 
SrO 
BaO 
.07 
trace 
.07 
trace 
.11 
trace 
.08 ; 
none 
Li.,0 
S0 3 
.06 
99.92 
100. 23 
100. 37 
99.96 
1 
! 
