94 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [no. 228. 
E. Ferruginous chert, sec. 28, T. 58 N., R. 17 W. 
F. Ferruginous chert, horizon of ore deposits, Oliver mine. 
G. Amphibolitic chert, Old Chicago mine. 
H. Amphibolitic chert, one-half mile southwest of Virginia. 
I. Amphibolitic chert, Donora mine. 
G, H, and I are largely amphibole in a matrix of chert. Analyses 
by George Steiger, record Nos. 1931, 19-18. 
Si0 2 
ALA 
Fe 2 3 
FeO 
MgO 
CaO 
Alkalies 
H 2 Oatl05° ... 
H 2 above 105 c 
Ti0 2 
co 2 
PA 
MnO 
C (organic) ... 
63.92 
none 
31. 13 
3.13 
.49 
none 
trace 
.48 
1.12 
trace 
none 
.05 
.10 
100.42 
32. 56 
none 
66. 02 
.30 
none 
.18 
none 
.32 
.90 
.16 
none 
.12 
.14 
G. 
100. 70 
50.36 
.64 
6.46 
32.91 
3.94 
.23 
none 
.27 
4.64 
none 
none 
none 
none 
.18 
99.63 
83. 82 
.39 
4. 46 
8.77 
none 
.60 
none 
.13 
1.37 
none 
.72 
.02 
none 
100. 28 
