162 
ANALYSES OF EOCKS, U. S. GEOLOGICAL SURVEY. 
[NO. 228. 
SECOND GROUP — ROCKS OF THE CRIPPLE CREEK DISTRICT. 
Described by Cross. Descriptions published, except when other- 
wise stated, in 16th Ann., Part II, pp. 38-50. Analyses, with two 
exceptions, which are properly noted, by W. F. Hillebrand, record 
Nos. 1418, 1153, and 1524. 
A. Phonolite, dike in granite northeast of Big Bull Mountain. 
Miaskose. Contains anorthoclase, nepheline, sodalite, segirine-augite, 
some segirine, biotite, magnetite, and limonite. Nosite not distin- 
guishable. P. R. C. 616. 
B. Phonolite, Mitre Peak. Miaskose. Contains sanidine, nephe- 
line, sodalite, segirine , nosite, and colorless particles which may be 
lavenite. P. R. C. 608. 
C. Phonolite, hill 1 mile south of Straub Mountain. Miaskose. 
Contains anorthoclase, sanidine, nepheline, sodalite, nosite, analcite, 
and aegirine, with sometimes segirine-augite. P. R. C. 612. 
D. Phonolite, Rhyolite Mountain. Miaskose. Contains nepheline, 
nosite, analcite, segirine, and some aegirine-augite, in a feldspathic 
groundmass. Sp. gr., 2.52, 23°. P. R. C. 618. 
E. Phonolite, between Florissant and Manitou. Miaskose. Analy- 
sis by L. G. Eakins, made in the Denver laboratory, inserted here for 
comparison with the Cripple Creek samples. Described by Cross in 
Proc. Colorado Sci. Soc.,vol. 2, p. 167. Contains sanidine, nepheline, 
hornblende, with accessory pyroxene (V), magnetite, apatite, and 
sphene. Sp. gr., 2.576, 13°. P. R. C. 607. 
F. The portion of E soluble in hydrochloric acid. This portion 
amounted to 25.39 per cent, and is reduced here to 100. Analysis by 
Eakins. 
A. 
B. 
C 
D. 
E. 
F. 
SiO., ..... 
59.00 
20.07 
1.58 
.65 
.10 
1.05 
8.34 
5.63 
.24 
2.03 
.29 
.05 
.20 
.12 
none 
trace 
trace 
.07 
.24 
.26 
99.92 
58.98 
20.54 
1.65 
.48 
.11 
.67 
9.95 
5.31 
.19 
.97 
.24 
.04 
.20 
.26 
none 
none 
trace 
.20 
.28 
58.78 
20.03 
1.87 
.49 
.16 
.83 
9.36 
5.50 
.31 
1.57 
.29 
.03 
.17 
.15 
none 
none 
trace 
.12 
.58 
58.64 
19.62 
2.17 
.42 
.37 
1.24 
8.39 
5.26 
.34 
2.40 
.20 
.03 
.09 
.20 
trace 
trace 
trace 
trace? 
.14 
.23 
60.02 
20.98 
2.21 
.51 
trace 
1.18 
8.83 
5.72 
} ;» 
44 66 
Al,() s ... 
31.59 
Fe 2 3 
.95 
FeO 
MgO 
CaO 
2 25 
Na 2 
18 42 
K 2 
2 13 
H 2 Oat 100° 
H 2 above 100° 
TiO., 
P 2 5 
trace 
Zr0 2 
MnO 
trace 
SrO 
BaO 
Li 2 
so 3 
CI 
trace 
co 2 
100. 07 
100. 24 
( .)!>. 74 
100. 15 
100. 00 
