68 
ANALYSES OF ROCKS, IT. S. GEOLOGICAL SURVEY. 
[bull. 168. 
J. Pre-Cambrian nonporphyritic metabasalt, from the Hemlock 
formation. Contains plagioclase, light-green hornblende, epidote- 
zoisite, chlorite, calcite, muscovite, apatite, sphene, quartz, pyrite, 
and magnetite. 
K. Porphyritic metabasalt, Hemlock formation. Same minerals 
as in J, with feldspar phenocrysts. 
L. Porphyritic metabasalt, like K. 
M. Metadolerite, large dike in T. 43 N., R. 31 W., east of Mansfield. 
Hitherto unpublished. Petrographic data furnished by C. R. Van 
Hise. Contains uralite, labradorite, and ilmenite. 
Analyses J, K, and L by H. N. Stokes, record No. 1617. 
Analysis M by George Steiger, record No. 1814. 
Si0 2 .. 
A1 2 3 . 
Fe 2 3 
FeO.. 
MgO. 
CaO.. 
Na 2 0. 
H 2 OatllO°-.. 
H 2 above 110 c 
Ti0 2 
P 2 5 
v 2 o 3 
Cr 2 3 
MnO 
CuO 
SrO 
BaO 
Li 2 
C0 2 
S 
46.47 
16.28 
3.15 
8.96 
6.56 
7.90 
3.64 
.21 
.28 
3.89 
1.28 
.13 
.01 
.09 
trace 
none 
none 
trace 
1.26 
none 
trace 
K. 
47.20 
15.36 
3.06 
8.87 
4.20 
5.05 
4.72 
1.40 
.16 
3.04 
3.30 
.36 
M. 
none 
.20 
trace 
trace 
trace 
trace 
3.34 
trace 
trace 
100. 11 
100. 26 
52.59 
15.89 
6.12 
3.96 
5.04 
5.55 
5.79 
.67 
.16 
2.16 
1.36 
.15 
.04 
trace 
.25 
trace 
none 
trace 
none 
none 
none 
trace 
44.29 
17.46 
3.82 
10. 35 
7.03 
8.68 
2.19 
.71 
.21 
4.11 
1.40 
.20 
trace 
none 
99.73 
100.45 
