42 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [no. 228. 
CONNECTICUT. 
A. Olivine-basalt, main flow, Pine Hill, South Britain. Auvergnose. 
Contains plagioelase, pink augite, olivine, and magnetite. The rock 
is (mite fresh. 
B. Olivine-basalt, anterior flow, South Britain. Contains plagio- 
clase, uralitized augite, olivine, and magnetite. Rock much altered, 
and containing numerous amygdules of calcite and prehnite stained 
by iron. 
Rocks A and B are described by W. H. Hobbs in 21st Ann. Rept, 
Part III, p. 60. Analyses by W. F. Hillebrand, record No. 1842. 
C. Basic pitchstone (tachylyte), from the so-called "ash bed" north- 
east of Meriden. SB. 1-2 of auvergnase. Described by Emerson in 
Bull. Geol. Soc. Amer., vol. 8, p. 77. Analysis by H. N. Stokes, 
record No. 1641. 
Si0 2 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 Oatl05°... 
H 2 above 105° 
Ti0 2 
PA 
NiO 
MnO. 
SrO 
BaO 
Li 2 
C0 2 
F 
FeS 2 orFe 7 S 8 «. 
52.40 
13.55 
2.73 
9.79 
5. 53 
10.01 
2.32 
.40 
.62 
1.05 
1.08 
.12 
trace 
.26 
none 
trace? 
none 
13 
99.99 
47.52 
13.91 
7.06 
3.76 
6.84 
5.71 
3.06 
.77 
1.75 
4. 55 
1.19 
.15 
trace 
.18 
none 
trace 
trace 
3.68 
100. 13 
46.86 
13.96 
5.23 
4.67 
7.69 
9.42 
1.85 
2.02 
1.29 
3.43 
1.13 
.15 
trace 
trace 
.03 
trace 
2.19 
trace 
).92 
a Calculated as pyrite. 
