64 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [no. 228. 
The following- rocks from Corundum Hill were collected, analyzed, 
and described by T. M. Chatard, Bull. 42, p. 45. 
I. Altered gneiss. Made up of micaceous scales, with grains of 
quartz and some earthy matter. Record No. 238. 
J. Dunite. Dunose. Olivine rock containing a little chromite. 
Record No. 256. 
K, L. Yellow, clay-like alterations of dunite. Record Nos. 254,255. 
Other analyses of altered rocks are given in the paper, and also 
analyses of associated minerals. 
I. 
J. 
K. 
L. 
Si0 2 . 
64.27 
16. 75 
6.08 
.89 
1.74 
.25 
.89 
3.09 
4.97 
1.32 
.05 
40.11 
.88 
1.20 
6.09 
48.58 
40.18 
1.35 
10.97 
40.04 
A1 2 3 
3.17 
Fe 2 3 
12.15 
FeO 
MgO 
43.84 
42.97 
CaO 
Na 2 
K 2 
H,0 (Ign. ) 
2.74 
2.01 
none 
2.14 
Ti0 2 
none 
P 2 5 
Cr 2 0, 
.18 
1.41 
MnO 
.07 
Chromite 
.56 
.17 
100. 37 
100. 34 
99.76 
100. 64 
