76 ANALYSES OF HOCKS, U. S. GEOLOOIOAL SURVEY. [no. 228. 
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. 27 W. 
Marquettose. Contains diallagc, olivine, magnetite, and plagioclase. 
The diallage is partly chloritized, and the olivine is partly serpent in- 
ized. Analysis by W. F. Hillebrand, record No. 1452. P. R. C. 996. 
B. Altered greenstone, Marquette district, t hmptonose. Analysis 
by George Steiger, record No. 1586, hitherto unpublished. P. R. C. 
988. 
C. Grunerite-magnetite-schist, sec, 11, T. 47 N., R. 27 W. Mainly 
impure grunerite, with magnetite and quartz. Analysis by W. H. 
Melville, record No. 1408. 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. 0, D, and E are similar schists, and 
alike in mineralogical composition. P. R. C. 981. 
Si0 2 . 
A1A 
Fe 2 0, 
FeO. 
MgO 
CaO 
Na 2 
K 2 
H 2 OatllO°.... 
H 2 above 110° 
Ti0 2 
PA 
Cr 2 3 
MnO 
NiO 
CuO 
SrO 
BaO 
C0 2 
S0 3 
39. 37 
4.47 
4. 96 
9. 13 
26. 53 
3.70 
.50 
.26 
.87 
7.08 
.66 
.17 
.68 
.12 
.21 
B. 
trace 
trace 
1.23 
99.94 
48. 85 
15. 83 
2.50 
10.71) 
5. 82 
6.20 
2.79 
1.31 
.27 
3.77 
1.28 
.22 
11 
.09 
none 
none 
.06 
99.89 
c. 
46.94 
.66 
4. 51 
:;:;. 72 
6.64 
3.22 
.16 
i). 
49.70 
1.35 
3.10 
37. 19 
5.72 
.68 
trace 
} • 
67 
none 
.07 
31 
2.79 
99.69 
1.40 
.12 
.93 
100. 19 
46. 25 
.92 
30.62 
16.92 
2.13 
1.69 
none 
none 
.42 
none 
.07 
1.01 
none 
trace 
none 
none 
none 
100. 03 
