TERTIARY VOLCANIC ROCKS-LATITE-PHONOLITE. 
79 
CHEMICAL CHARACTER. 
The accompanying analyses show the chemical character of the latite-phonolites, 
their range in composition, and their relation to the phonolites: 
Analyses of latite-phonolites from Cripple Creek. 
I. 
II. 
III. 
IV. 
V. 
VI. 
VII. 
5G. 01 
58.05 
54.88 
54. 43 
62.79 
59.38 
58.85 
AljOs. 
17.92 
17.66 
18.53 
19.01 
19.10 
19. 47 
20.06 
FejOa., 
4.20 
3.51 
2.93 
2.85 
2.29 
1.60 
' 1.83 
FeO. 
2.52 
1.65 
1.92 
1.93 
.36 
1.19 
.51 
MgO. 
2.04 
1.55 
1.26 
.99 
.40 
.36 
.18 
CaO. 
4.80 
4.58 
4.15 
4.33 
.87 
1.96 
.95 
Na 2 0. 
4.92 
5.80 
6.65 
6.92 
6.23 
7.80 
9.01 
k 2 o. 
4.21 
4.06 
4.90 
5.07 
5.58 
5.83 
5.43 
H 2 0 -. 
.31 
.35 
.38 
.31 
.25 
.11 
.27 
h 2 o +. 
1.10 
.87 
1.75 
1.68 
.84 
.69 
1. 74 
Ti0 2 . 
1.20 
.91 
.93 
.96 
.71 
.58 
.25 
Zr0 2 . 
.02 
.02 
.03 
.04 
.02 
.10 
.16 
C0 2 . 
None. 
None. 
. 13 
. 14 
. 12 
p 2 o 5 . 
.55 
.40 
.27 
.25 
.12 
.08 
.04 
so 3 . 
None. 
.04 
.36 
.42 
None. 
.37 
.10 
Cl. 
Trace. 
Trace. 
.14 
.22 
Trace. 
.22 
.31 
'.04 
None. 
. 10 
.07 
.10 
Cr 2 0;. 
None. 
None. 
NiO. 
None. 
n. d. 
MnO. 
.13 
.13 
.25 
.08 
.07 
.15 
.18 
BaO. 
.16 
.19 
.18 
.21 
.14 
.13 
Trace. 
SrO. 
.06 
.08 
.11 
.21 
.03 
.03 
Trace. 
Li 2 0. 
Trace. 
Trace. 
Trace. 
Trace. 
Trace. 
100.19 
99.75 
99.82 
100.07 
99.90 
100.05 
99.98 
I. Latite-phonolite, Portland mine, level 6. 
II. Latite-phonolite, Anaconda mine, adit level. 
III. Latite-phonolite, Portland mine, adit level. 
IV. Latite-phonolite, 3,300 feet S. 10° E. from Bull Cliff. 
V. Biotite trachyte, Portland mine, 500-600 foot level. 
VI. Latite-phonolite, south slope. Bull Cliff. Cf. Cross, W., Sixteenth Ann. Rept. U. S. Geol. Survey, pt.2,1895,p. 43. 
VII. Average analysis of Cripple Creek phonolites (V of table on p. 66). 
Analyses I and II by George Steiger; III-VI by W. F. Hillebrand. 
I. A gray rock, showing numerous small phenocrysts of pyroxene and a few 
of feldspar in a fine-grained groundmass. The microscope shows the larger feld¬ 
spar crystals to be between oligoclase and andesine, often bordered by orthoclase. 
The pyroxene is pale green, slightly pleocliroic, and has a large extinction angle. 
Aggregates of pyroxene and magnetite grains in some cases possess the outline of 
hornblende, while in others the resorption is seen to be destroying biotite. Some 
large grains of magnetite and large apatite crystals are present. All these are 
contained in a predominant trachytic groundmass which is a little decomposed, but 
seems to be made up almost exclusively of orthoclase laths, with a very small amount 
of sodalite in tiny grains. Analcite can not be identified. This facies is closely 
related to the latites and is the extreme in that direction of the latite-phonolite 
type. It occurs in the Portland mine, but has been found in few other places. The 
specimen is slightly decomposed. • 
