70 ANALYSES OF EOCKS, U. S. GEOLOGICAL SURVEY. [bull. 168. 
3. MENOMINEE RIVER. 
1st. sturgeon falls cjabbro. 
From Sturgeon Falls. Menominee River, sec, 27, T. 39 N., R. 29 W., 
Michigan. Described by Williams, Bull. 62, p. 67. 
A. Saussurite-gabbro. Contains plagioclase, almost wholly altered 
to saussurite, diallage, hornblende, and ilmemte, with quartz, calcite, 
and chlorite as alteration products. 
B. The same, altered and somewhat schistose. Feldspar much 
altered into calcite, with secondary quartz and sericite; pyroxene and 
hornblende changed to chlorite. Leucoxene common. 
C. Light-gray, silvery schist, derived from gabbro. Contains chlo- 
rite, calcite, and a little quartz, with remnants of feldspar and some 
leucoxene. Analyses by R. B. Riggs, record Nos. 389, 390, 391. Mate- 
rial dried at 105°. Ti0 2 undetermined. 
Si0 2 . 
A1 2 3 
Fe 2 3 
FeO. 
MgO 
CaO. 
Na 2 
K 2 0. 
H 2 0. 
C0 2 . 
51.46 
14.35 
3.90 
5.28 
9.54 
9.08 
2.92 
.24 
3.30 
.20 
100. 27 
38.05 
24.73 
5.65 
6.08 
11.58 
1.25 
2.54 
1.94 
7.53 
.93 
100. 28 
c. 
45.70 
16.53 
4.63 
3.89 
9.57 
4.28 
.55 
3.82 
4.70 
5.95 
99.62 
