166 ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [bull. 168. 
UTAH. 
I. ROCKS FROM THE TINTIC DISTRICT. 
Described by Tower and Smith in 19th Ann., Part III, pp. 609 et seq. 
Analyses by Stokes, record No. 1746. 
A. Gray, porphyritic rhyolite, south of Pinyon Creek. Contains 
phenocrysts of sanidine, quartz, biotite, plagioclase, and hornblende; 
the last mineral sparingly. Also tridymite, magnetite, apatite, zircon, 
and a small amount of glassy residue. 
B. Quartz-porphyry, Swansea mine. Phenocrysts of feldspar and 
quartz, the orthoclase somewhat altered. Microscopic biotite occurs 
sparingly. Also contains magnetite, apatite, zircon, a little chlorite, 
and secondary pyrite. 
C. Andesite, Tintic Mountain. Phenocrysts of biotite and feldspar. 
Contains plagioclase, chiefly labradorite, augite, biotite, hypersthene, 
magnetite, and apatite, in a dark-gray glass. 
D. Granular monzonite, Iron Duke mine. Contains orthoclase, 
plagioclase, quartz, hornblende, biotite, magnetite, apatite, zircon, and 
titanite, with a little chlorite and epidote. 
E. Altered monzonite, near Tintic mine. Feldspar and ferromag- 
nesian minerals completely altered. Rutile is present; quartz seems 
to have been added. 
A. 
B. 
c. 
D. 
E. 
Si0 2 
69.18 
14. 36 
2.52 
.57 
.70 
1.88 
3.58 
5.00 
.35 
.25 
.69 
.26 
trace 
.01 
.10 
.09 
trace 
trace 
none 
none 
none 
71.56 
14.27 
, - .89 
.42 
1.18 
•3.00 
4.37 
.36 
.79 
.38 
.13 
trace 
.01 
trace 
.28 
trace 
none 
none 
60.17 
15.77 
3.42 
2.95 
2.52 
4.69 
2.96 
4.16 
.25 
1.23 
.87 
.40 
none 
.01 
.11 
.14 
.09 
trace 
none 
none 
none 
59.76 
15.77 
3.77 
3.30 
2.16 
3.88 
3.01 
4.40 
.31 
1.11 
.87 
.42 
none 
.02 
.12 
.09 
trace 
trace 
.78 
none 
none 
71.14 
16.22 
.94 
.16 
1.12 
.25 
.07 
4.96 
.49 
2.74 
.75 
.32 
none 
.02 
trace 
.05 
trace 
trace 
none 
ALjDa 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 OatllO° 
H 2 above 110° 
Ti0 2 
P 2 5 
Cr 2 3 
V 2 3 
MnO 
BaO 
SrO 
Li 2 
CO, 
S 
so 3 
.26 
FeS 2 
2.29 
.06 
CI 
trace 
.04 
.04 
trace 
99.54 
99.99 
99.78 
99.81 
99.49 
Fluorine was not looked for in the analyses. 
