102 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[NO. 228. 
The four following- rocks, from Sundance quadrangle, were collected 
by W. 8. Tangier Smith, who has supplied the petrographic data. 
Analyses by George Steiger, record No. 1999. Hitherto unpublished. 
O. Syenite-porphyry. Pulaskose. Contains phenocrysts of ortho- 
clase, segirine- augite, a little augite, nepheline (?), magnetite, garnet, 
titanite, and apatite. Groundmass mainly feldspar, probably ortho- 
clase, and other minerals as abov r e, with possibly some species of the 
sodalite group. 
P. Essexite-porphjay. Essexose. Contains phenocrysts of feld- 
spar, apparently orthoclase and anorthoclase, regirine-augite or little 
augite, garnet, probably nosean, titanite, magnetite, and apatite. In 
the groundmass, feldspar (orthoclase ?), regirine-augite, and possibly 
sodalite. 
Q. Syenite-porplryry. Aherose-laurvikose. Contains phenocrysts 
of feldspar (orthoclase and plagioclase?), aegirine-augite, magnetite, 
titanite, and apatite. In the groundmass, feldspar, magnetite, aegirine- 
augite, and apatite. 
R. Porphyritic rock. Kentallenose. Contains phenocrysts of 
augite, magnetite, apatite, biotite, orthoclase, and plagioclase. Same 
minerals in the groundmass, with perhaps some species of the 
nepheline-sodalite group. 
Si0 2 55. 14 
ALA 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
H 2 at 105° 
H 2 above 105° 
Ti0 2 
PA 
so 3 
CI 
s 
MnO.. ! trace 
BaO 
18.98 
2.60 
1.62 
.32 
3.96 
5.38 
6.64 
.63 
3.70 
.50 
.17 
.10 
trace 
.03 
Less O 
99. 
(il 
99. 76 
57.46 
18.41 
2.40 
1.28 
none 
4.02 
9.23 
4.93 
.45 
1.12 
.42 
.11 
.50 
.23 
.05 
.11 
none 
100. 72 
.08 
100. 64 
58.08 
18.38 
3.02 
1.42 
.96 
3.85 
6.22 
5.11 
.37 
1.55 
.58 
.21 
.07 
trace 
none 
.10 
none 
99.92 
42.95 
12.44 
10.16 
5.18 
5.82 
13. 11 
2.10 
2.29 
.91 
1.98 
1.34 
1.37 
.15 
.07 
none 
.29J 
none 
100. II 
.021 
100. 1' 
No C0 2 in any of these rocks. 
