288 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
F. Neocomian shale, altered, light brown, friable. From near 
Arroyo del Cerro. 
G. Calcareous shale, near Arroyo del Cerro. Hard, compact, dark 
colored. Very much altered. 
H. Red shale, metamorphic area at head of Bagley Creek. 
I. Silicified shale or phthanite, same locality as H. 
J. Clay slate, near the head of Yaqui Gulch, in Mariposa County. 
Described by Turner in Bull. 150, p. 342. Contains grains of quartz 
and feldspar, abundant carbonaceous particles, a chloritic substance (?), 
and a fibrous alteration of sillimanite ( ?). Analysis by George Steiger, 
record No. 1643. 
F. 
G. 
H. 
I. 
J. 
Si0 2 
45.64 
15.42 
3.40 
3.73 
4.62 
8.11 
3.13 
1.86 
| 8.74 
44.56 
3.12 
1.27 
5.21 
3.39 
12.70 
3.09 
.88 
1.41 
6.24 
69. 98 
11.69 
6.23 
1.08 
1.29 
.38 
.73 
3.72 
1.03 
2.92 
93.54 
2.26 
.48 
.79 
.66 
.09 
.37 
.51 
.21 
.72 
60.35 
17.62 
5.64 
2.20 
1.04 
.45 
1.00 
3.16 
1.02 
4.36 
.75 
.17 
ALO s 
Fe 2 O s 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 at 100° 
H 2 above 100° 
Ti0 2 
P.,0* 
.27 
.12 
.33 
.16 
.05 
Cr 2 3 
MnO 
trace 
.49 
.23 
none 
.12 
none 
.05 
.01 
trace 
1.72 
BaO 
C0 2 . 
4.59 
17.62 
so 3 
CI 
F 
c 
99.96 
99.65 
99.59 
99.86 
99.76 
