48 
ANALYSES OF EOCKS, U . S. GEOLOGICAL SURVEY. 
[NO. 228. 
PENNSYLVANIA. 
A. Aporhyolite, Monterey, Franklin County. Jiallerudose. De- 
scribed by Florence Bascom in Bull. 150, p. 343. Contains alkali feld- 
spar, quartz, -sericite, epidote, titaniferous magnetite, leucoxene, and 
rarely sphene. Analysis by H. N. Stokes, record No. 1479. P. R. C. 136. 
B. Quartz-porphyry, same locality. Alaskose. Analyzed for G. H. 
Williams, but never described. Analysis by L. G. Eakins, record 
No. 1350. 
C. Arkose-gneiss. Yellowstonose. Contains quartz, orthoclase, mic- 
rocline, oligoclase, biotite, hornblende, magnetite, and minor acces- 
sories. 
D. Mica-gneiss. III. S. 2. S. Consists chiefly of quartz and musco- 
vite, with feldspars and minor accessories. 
E. Hornblende-gneiss. Auvergnose. Contains largely green horn- 
blende and colorless anthophyllite, with plagioclase, magnetite, and 
scanty secondary quartz. 
F. Hypersthene-gabbro. Ilessose. Contains quartz, orthoclase, 
labradorite, diallage, hypersthene, magnetite, apatite, and minor acces- 
sories. 
Rocks C to F are average samples collected by F. Bascom within the 
Philadelphia quadrangle. Analyses by W. F. Hillebrand, record No. 
1872. The mica-gneiss is described in the Cecil County volume of the 
Maryland Geological Survey. 
Si0 2 
A1 2 3 
FeA 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 Oat 100°.... 
H 2 above 100° 
Ti0 2 
Zr0 2 
C0 2 
Cr 2 3 
MnO 
NiO 
PA 
s 
BaO 
SrO 
LLO 
76. 34 
11.60 
2.41 
.30 
.06 
. 55 
5. 50 
2.75 
.10 
.39 
.26 
trace 
B. 
73. 85 
13. 15 
3.27 
.36 
.32 
.82 
2.29 
5.42 
.71 
trace 
09 
trace 
09 
100. 35 
06 
100. 34 
70.21 
13.95 
1.05 
:;. os 
1 . 26 
3. 10 
3.27 
2.69 
.19 
.48 
.52 
trace 
. 11 
.11 
trace? 
.10 
.09 
.09 
trace 
trace? 
100. 30 
60. 13 
15.11 
2. 52 
:;. 19 
2.42 
1.87 
2.71 
2.86 
.24 
1.55 
.82 
(?) 
none 
.20 
trace 
.22 
.03 
trace 
trace 
none 
E. 
48. 68 
14.39 
4.00 
10.09 
6. 32 
9.23 
2.31 
.47 
.46 
2.03 
1.69 
(?) 
none 
.22 
trace 
.29 
trace 
trace 
none 
trace? 
99.87 
54.03 
16.71 
1.37 
7.70 
5.66 
8.84 
2.99 
.67 
.14 
.53 
.84 
(?) 
.40 
trace 
.13 
trace 
.13 
.09 
trace 
trace 
trace? 
100.18 [ 100.23 
