98 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[NO. 228. 
SOUTH DAKOTA. 
A. Phonolite, Black Hills. Miaskose. Described bv Whitman Cross 
in Bull. 150, p. 191. Contains sanidine, nephelite, aegirite, 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 
constituents. 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. 
D. Volcanic ash, 3 miles west of Argyle, Custer County. Amiatose. 
Collected by N. H. Darton. Analysis by George Steiger, record 
No. 1875. 
A. 
B. 
C. 
D. 
Si0 2 
57.86 
58.60 
20.98 
2.22 
.44 
.33 
1.13 
8.38 
5.49 
66.77 
17.65 
1.55 
3.29 
2.13 
.56 
.99 
4.49 
64.47 
14.74 
2.73 
.78 
.29 
4.00 
2.55 
3.31 j 
.93 j 
4.78 
.76 
.29 
A1 2 3 
20.26 
2.35 
.39 
.04 
.89 
9.47 
Fe»0, 
FeO 
MgO 
CaO 
Na 2 
K 2 
5.19 
.21 
2.40 
.22 
.03 
H 2 at 110° 
, 
H 2 above 110° 
Ti0 2 
P 2 5 
\ 1.92 
1.89 
Zr0 2 
.15 
.21 
MnO 
.20 
SrO 
.04 
.09 
trace 
.06 
03 
BaO 
.13 ( 
Li 2 
S0 3 V 

S 
| 
CI 
.08 
F 
(?) 
none 
co 2 

99.97 
99.69 
99.32 
99. 76 1- 
