188 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [no. 228. 
UTAH. 
1. ROCKS FROM THE TINTIC DISTRICT. 
Described by Tower and Smith in 19th Ann., Part III, pp. 609 et seq. 
Analyses by Stokes, record No. 1716. 
A. Gray, porphyritic rhyolite, south of Pinyon Creek. Toscanose. 
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. P. R. C. 1039. 
P>. Quartz-porphyry, Swansea mine. Toscanose. Phenocrysts of 
feldspar and quartz, the orthoclase somewhat altered. Microscopic 
biotite occurs sparingly. Also contains magnetite, apatite, zircon, a 
little chlorite, and secondary pyrite. P. R. C. 1010. 
C. Andesite, Tintic Mountain. Harzose. Phenocrysts of biotite 
and feldspar. Contains plagioclase, chiefly labradorite, augite, biotite, 
hypersthene, magnetite, and apatite, in a dark-gra} T glass. P. R. C. 
1036. 
D. Granular monzonite, Iron Duke mine. Harzose. Contains ortho- 
clase, plagioclase, quartz, hornblende, biotite, magnetite, apatite, zir- 
con, and titanite, with a little chlorite and epidote. P. R. C. 1032. 
E. Altered monzonite, near Tintic mine. Feldspar and ferromag- 
nesian minerals completely altered. Rutile is present; quartz seems 
to have been added. 
Si0 2 .. 
A1 2 3 . 
FeA 
FeO.. 
MgO. 
CaO.. 
Na.,0 . 
K 2 
H 2 OatllO°._. 
H 2 above 110 c 
Til) 
PA 
CrA- — 
V 2 3 
MnO 
BaO 
SrO 
Li 2 
co 2 
s 
so 3 
FeS, 
ci.: 
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 
trace 
99.54 
71.56 
14.27 
.89 
.42 
1.18 
3.00 
4.37 
.36 
.79 
.38 
.13 
trace 
.01 
trace 
.28 
trace 
none 
none 
2.29 
.06 
99. 99 
60. 17 
15.77 
3.42 
95 
52 
69 
96 
16 
.25 
1.23 
.87 
.40 
none 
.01 
.11 
.14 
.09 
trace 
none 
none 
none 
04 
99. 78 
59. 76 
15. 77 
3.77 
3.30 
3.01 
4.40 
.31 
1.11 
.87 
.42 
none 
.02 
.12 
.09 
trace 
trace 
.78 
none 
none 
.04 
99. 81 
71. 14 
16.22 
.94 
.16 
1.12 
.25 
.07 
4.96 
.49 
2.74 
.75 
.32 
none 
.02 
trace 
.05 
trace 
trace 
none 
26 
trace 
99. 49 
Fluorine was not looked for in the analyses. 
