CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
87 
The following analyses, by W. F. Hillebrand, of separations from 
the gabbro of Ashland County, Wis., were made for the late K. D. 
Irving, but were never published by him: 
H. Magnetite, record No. 687. Partial analysis. 
I. Feldspar, record No. 688. 
J. Diallage, record No. 686. 
For convenience I also include here, although it is decidedly out of 
classification — 
K. Graywacke, Hurley, Wis. Described by Bay ley in Bull. L50, 
p. 84. Analysis by H. N. Stokes, record No. 1314. Contains quartz, 
feldspars, iron oxides, and probably kaolin. In the cement are chlo- 
rite, quartz, magnetite, pyrite, rutile, occasionally biotite, and either 
muscovite or kaolin. P. R. C. 20. 
Si0 2 . 
Fe 2 3 
FeO.. 
MgO. 
CaO.. 
Na 2 0. 
K 2 0.. 
Ti0 2 
PA 
MnO 
SrO. 
BaO. 
LLO 
ii. 
50.29 
30.70 
77 
53.30 
29.03 
.55 
.23 
.13 
11.40 
4.87 
.40 
.23 
trace 
trace 
none 
trace 
trace 
none 
89. 40 100. 14 
49. 80 
2.86 
2.48 
10.82 
15. 33 
16.50 
.51 
.12 
.33 
1.29 
trace 
.37 
none 
none 
trace? 
K. 
76. 84 
11.76 
.55 
2.88 
1.39 
.70 
2.57 
1.62 
1.87 
trace 
100.41 100.18 
