280 ANALYSES OF ROCKS, U. S GEOLOGICAL SURVEY. [no.22& 
L WINNEBAGO COUNTY, IOWA. 
Fell May 2, 1890. Sp. gr., 3.804, 28°.5. Analyzed by L. G. Eakins, 
record No. 1190, and described in Bull. 78, p. 95. 
( 'omposition of the mass. 
Nickel-iron 19. 40 
Troilite - 6. 19 
Soluble silicates 36. 04 
I nsoluble silicates 38. 37 
100. 00 
Separate analyses : 
A. The nickel-iron. 
B. Silicate soluble in hydrochloric acid, calculated to 100 per cent. 
C. Insoluble silicate, recalculated to 100 per cent. The Cr 2 3 prob- 
ably represents chromite. 
A. 
B. 
c. 
Fe 
92.65 
6.11 
.65 
trace 
trace 
Si0 2 
39. 74 
55. 51 
Ni 
A1 2 3 
5.43 
Co 
Cr 2 3 
.25 
P 
FeO 
NiO 
18.42 
.38 
9.45 
S 
MnO 
trace 
CaO 
.69 
40.77 
trace 
trace 
trace 
3.00 
MgO 
24.09 
K 2 
.15 
Na 2 ( ) 
2. 12 
r 2 o 5 
99. 41 
100. 00 
100.00 
