226 
ANALYSES OF EOCKS, IT. S. GEOLOGICAL SURVEY. 
[bull. 1G8. 
ALASKA. 
Rocks A to H, inclusive, were collected by G. F. Becker, who fur- 
nishes the petrographic data. A, B, C, D, F, and H are described by 
Becker in the 18th Ann., Part 3, p. 7. Analyses by Hillebrand, record 
No. 1585. 
A. Augite-bronzite-andesite, Delarof Harbor, Unga Island. Green- 
ish black. Contains plagioclase, near labradorite, with much smaller 
proportion of augite and bronzite, in a groundmass of plagioclase, with 
a little glass and much light-green indeterminate material. Contains 
0.04 V 2 3 . 
B. Augite-bronzite-andesite, St. Augustine Volcano, Cook Inlet. 
Purplish gray. Contains labradorite, augite, and bronzite, in a ground- 
mass of plagioclase and magnetite. 
C. Quartz-porphyry, bed of Bear Creek, 4 miles from its mouth, 
Turnagain Arm, Cook Inlet. Resembles D, with more feldspar and 
less quartz. 
D. Quartz-porphyry, east of mouth of Indian River, Sitka, Baranof 
Island. Contains plagioclase, quartz, a little pyroxene, and some car- 
bonaceous matter, with secondary quartz, calcite, and muscovite. 
E. Diorite, head of Captains Bay, Unalaska Island. Contains 
plagioclase, biotite, hornblende, chlorite, magnetite, and sometimes 
tourmaline. 
Si0 2 
A1A 
FeA 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 OatllO°.... 
H 2 above 110° 
Ti0 9 
NiO. 
MnO 
SrO . 
BaO. 
C0 2 
C .. 
FeS 9 
A. 
56. 63 
16.85 
3.62 
3.44 
4.23 
7.53 
3.08 
2.24 
.80 
.51 
.67 
.16 
trace? 
.23 
trace 
.09 
trace 
none 
06 
100. 14 
B. 
60.40 
16.89 
1.88 
3.72 
3.82 
7.25 
3.80 
. 77 
.09 
.20 
.61 
.16 
.02 
.12 
trace 
.06 
trace 
none 
08 
99.87 
62.92 
14.29 
.84 
4.66 
3.14 
2.72 
4.30 
1.39 
.22 
2.84 
.84 
.13 
trace 
.15 
trace 
.10 
trace 
1.24 
32 
100. 10 
I). 
65.94 
13.74 
.49 
5.21 
2.33 
2.87 
2.80 
1.63 
.21 
2.59 
.80 
.21 
trace? 
.11 
trace? 
.12 
trace 
.59 
.20 
.41 
100. 25 
E. 
58. 63 
16.23 
1.91 
4.20 
4.28 
6.59 
3.51 
2.09 
.15 
1.17 
.74 
.20 
.02 
.11 
trace 
.06 
trace 
none 
.04 
99.93 
