64 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
LAKE SUPERIOR REGION. 
1. MARQUETTE REGION, MICHIGAN. 
Rocks mostly described by Van Hise and Bayley. When not other- 
wise specified the descriptions have been published in Mon. XXVIII, 
and partly in 15th Ann., p. 485. 
A. Peridotite, near Opin Lake, E. \ sec. 27, T. 48 N., R. 21;°' 
Contains diallage, olivine, magnetite, and plagioclase. The dialla^ 
is partly chloritized, and the olivine is partly serpentinized. Analysi 
by W. F. Hillebrand, record No. 1452. P. R. C. 996. 
B. Altered greenstone, Marquette district. Analysis by George 
Steiger, record No. 1586, hitherto unpublished. P. R. C. 988. 
C. Griinerite-magnetite-schist, sec. 11, T. 47 N., R. 27 W. Mainly 
impure griinerite, with magnetite and quartz. Analysis by W. H. 
Melville, record No. 1403. P. R. C. 984. 
D. Like C, from sec. 18, T. 47 N., R. 28 W. Analysis by Melville, 
record No. 1403. P. R. C. 980. 
E. Like C and D, from sec. 20, T. 46 N., R. 30 W. Analysis by 
H. N. Stokes, record No. 1546. C, D, and E are similar schists, and 
alike in mineralogical composition. 
» 
A. 
B. 
c. 
D. 
E. 
Si0 2 
39.37 
4.47 
4.96 
9.13 
26.53 
3.70 
.50 
.26 
.87 
7.08 
.66 
.17 
.68 
.12 
.21 
48.85 
15. 83 
2.50 
10.79 
5.82 
6.20 
2.79 
1.31 
.27 
3.77 
1.28 
.22 
46.94 
.66 
4.51 
33.72 
6.64 
3.22 
.16 
49.70 
1.35 
3.10 
37.19 
5.72 
.68 
trace 
46.25 
.92 
30.62 
16.92 
2.13 
1.69 
none 
none 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 at 110° 
| .67 
none 
.07 
| 1.40 
H 2 above 110° 
Ti0 2 
.42 
none 
.07 
P,0, 
.12 
Cr 2 3 
MnO 
.11 
.31 
.93 
1.01 
none 
trace 
none 
none 
none 
NiO 
CuO .*. 
SrO 
trace 
trace 
1.23 
.09 
none 
none 
.06 
BaO- 
co 2 
2.79 
so 3 
99.94 
99.89 
99.69 
100. 19 
100.03 
