30 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[NO. 228. 
In these rocks the sulphur is all reckoned as p3 r rite, although 
pyrrhotite also is probably present. The carbonic acid represents 
either dolomite or siderite; not calcite. Traces of lithia and strontia 
occur in nearly all. Samples H, L, O, and Q contain traces of copper. 
In N there is 0.03 V 2 3 , a supplementary determination by Hillebrand. 
2. MISCELLANEOUS ROCKS. 
A. Amphibolite, Guilford. Described by Emerson in Mon. XXIX. 
Contains hornblende needles, with albite and rutile. Analysis by L. G. 
Eakins, record No. 1326. 
B. Granitoid gneiss, north of Lincoln's. 
C. The same, west slope of Little Peco. 
D. Chloritic granite. Yellowstonose. East Clarendon section. 
E. Hornblende-granite. Hessose. East Clarendon. 
Rocks B, C, D, and E collected by C. L. Whittle, but not described. 
Analyses by H. N. Stokes, record No. 1396. 
Si0 2 . 
A1 2 3 
Fe 2 3 
FeO. 
MgO 
CaO. 
Na 2 
K 2 0. 
H 2 0. 
Ti0 2 
PA 
Cr 2 3 
MnO 
BaO . 
49. 16 
16.43 
3.92 
7.19 
8.19 
9.21 
3.70 
.41 
.45 
1.03 
.16 
trace 
.23 
.02 
100. 10 
71.02 
15.00 
1.12 
1.81 
.69 
.31 
2.48 
5. 79 
1.14 
.35 
.13 
trace 
trace 
99.84 
c. 
69.97 
14.90 
2.16 
.96 
.37 
.45 
2.85 
6.54 
.66 
.44 
.12 
trace 
.09 
51 
67. 33 
16.20 
1.40 
2.73 
1.31 
2.81 
3.15 
2.14 
1.84 
.80 
.16 
trace 
.05 
99.92 
52. 
18. 
2. 
6. 
4. 
7. 
3. 
1. 
2. 
1. 
23 
99.83 
