84 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
SOUTH DAKOTA. 
A. Phonolite, Black Hills. Described by Whitman Cross in Bull. 
150, p. 191. Contains sanidine, nephelite, segiriie, nosean, and 
sodalite, with accessory sphene, apatite, and zircon, and possibly some 
rare zirconates or titanates. Also, sparingly, secondary zeolites and 
calcite. No magnetite, but minute ferritic flakes are disseminated 
through the rock. Analysis by W. F. Hillebrand, record No. 1618. 
P. R. C. 73. 
B. An earlier analysis of A, by H. N. Stokes, record No. 1314. 
This was made along the ordinary lines as regards "completeness," as 
requested by the collector, and without regard to minor accessory con- 
stituents. It serves well to illustrate the difference between the two 
modes of treatment, in comparison with the fuller analysis, 
C. Tourmaline-biotite-schist, north of Harney Peak, Black Hills. 
Described by Bayley in Bull. 150, p. 327. Contains quartz, biotite, 
tourmaline, a little garnet and rarely muscovite, iron ore, and apatite. 
Analysis by Stokes, record No. 1296. P. R. C. 130. 
A. 
B. 
c. 
Si0 2 
57.86 
20.26 
2.35 
.39 
.04 
.89 
9.47 
5.19 
.21 
2.40 
.22 
.03 
.15 
.21 
.04 
.09 
trace 
.06 
.03 
.08 
(?) 
none 
58.60 
20.98 
2.22 
.44 
.33 
1.13 
8.38 
5.49 
| 1.92 
66.77 
17.65 
1.55 
3.29 
2.13 
.56 
.99 
4.49 
| 1.89 
A1 2 3 * 
Fe 9 (X 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 at 110° 
H 2 above 110° 
Ti0 2 
P 2 5 
Zr0 2 
MnO 
.20 
SrO 
BaO 
Li 2 
S0 3 
S 
CI 
F 
C0 2 
99.97 
99.69 
99.32 
