346 ANALYSES OF ROCKS, IT. S. GEOLOGICAL SURVEY. [no. 228. 
MINNESOTA. 
Slates from the Mesabi district, described by C. K. Leith in Mon. 
XLIII. Analyses by George Steiger, record Nos. 1931, 1992. 
A. Typical " Virginia slate." Average sample. About half chlo- 
rite, with quartz and perhaps some feldspar fragments. 
B. Siliceous slate, from contact with gabbro, north of Birch Lake. 
C. Slaty phase of the iron formation, Moss mine. 
A. 
B. 
c. 
SiOo 
62.26 
16.89 
1.76 
4. 55 
2.95 
.42 
2.29 
3.02 
.70 
3.88 
.60 
none 
.20 
78. 95 
none 
13.89 
1.23 
.18 
.81 
none 
none 
.73 
2.21 
none 
1.59 
.04 
.11 
37. 11 
A1 2 3 
2.41 
Fe,0, 
17. 51 
FeO 
26. 13 
MsO - 
3.70 
CaO 
.75 
Na 2 
.09 
K 2 
.62 
H 2 at 105° . 
.95 
H 2 above 105° 
2. 57 
TiO, 
.22 
co 2 
6.16 
p.,o« 
.09 
Mn( ) 
1.21 
present 
.73 
99.52 
99. 74 
100.25 
