80 
ANALYSES OF ROCKS, U. S. GEOLOGJCAL SURVEY. 
[NO. 228. 
J. Pre-Cambrian nonporphyritic metabasalt, from the Hemlock 
formation. Beerbachose. Contains plagioclase, light-green horn- 
blende, 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. SR. 5 of monzonase. 
M. Metadolerite, large dike in T. 43 N., R. 31 W., east of Mansfield. 
Auvergnose. Hitherto unpublished.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 
ALA 
FeA 
FeO 
MgO 
CaO 
Na 2 () 
K 2 
H 2 Oatll0°.... 
H 2 above 110° 
Ti0 2 
PA 
VA 
CrA 
MnO 
CuO 
SrO 
BaO 
Li,0 
C0 2 
S 
F 
J. 
K. 
46. 47 
47.20 
16.28 
15. 36 
3.15 
3.06 
8.96 
8.87 
6.56 
4.20 
7.90 
5.05 
3. 64 
4.72 
.21 
1.40 
.28 
.16 
3.89 
3. 04 
1.28 
3. 30 
.13 
.36 
.01 
none 
.09 
.20 
trace 
trace 
none 
trace 
none 
trace 
trace 
trace 
1.26 
3.34 
none 
trace 
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 
99.73 
M. 
44. 29 
17.46 
3.82 
10.35. 
7.03 
8.68 
2.19 
.71 
.21 
4.11 
1.40 
.20 
trace 
100. 45 
