1(54 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [no. -228. 
THIRD GROUP. MISCELLANEOUS ROCKS. 
Analyses, elsewhere unpublished, exeept when otherwise stated, by 
W. F. Hillebrand, record Nos. 1448, 1453, and 1669. Petrographic 
data supplied by Whitman Cross. Names marked with a query are 
provisional designations onl} T . 
A. Trachyte?, near RobbinsV ranch. Toscanose. Has scattered 
phenocrysts of alkali feldspar, oligoclase, and biotite in a predomi- 
nant trachytic groundmass of alkali feldspar, trid}anite, particles of 
residual glass, and ferritic flakes and grains. P. R. C. 1326. 
B. Trachyte?, Wicher Mountain. Toscanose. Shows biotite and 
a few glassy feldspars in a groundmass resembling that of A. P. R. C. 
1328. 
C. Andesite?, Bare Hills. Palaskose. Composed mainly of plagio- 
clase and alkali feldspar, with small augites and much ferritic matter. 
Minute prisms of a yellowish brown amphibole (?) and scales of tridy- 
mite are also visible. P. R. C. 1327. 
D. Pyroxene-andesite?, Wicher Mountain. Monzonose. Contains 
phenocrysts of plagioclase, a few of augite, minute specks of iddings- 
ite, and Hakes of limonite. In the groundmass are plagioclase, ortho- 
clase (?), augite, iddingsite, and hypersthene. In the pores tridymite 
appears. P. R. C. 1325. 
E. Plagioclase-basalt?, mesa east of Mac Gulch. Andose. Con- 
tains plagioclase, augite, olivine, iddingsite, magnetite, biotite, and 
apatite. P. R. C. 1324. 
F. Plagioclase-basalt, Saddle Mountain. Andose. Phenocrysts of 
augite and olivine in a groundmass of plagioclase, orthoclase, augite, 
magnetite, biotite, and apatite. Very fresh. See Cross, Journ. Geol., 
vol. 5, p. 684. P. R. C. 1323. 
Si0 2 
Al 2 <) 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 Oatl00°._. 
H 2 above 100 c 
Tib 2 
PA 
Zr0 2 
VA 
MnO 
SrO 
BaO 
80 3 
C0 2 
69.52 
15.44 
1.90 
.09 
.17 
1.70 
4.54 
5.04 
.33 
.27 
.23 
.14 
.05 
.08 
.04 
.19 
17 
99.90 
66.12 
17.21 
2.43 
trace 
.35 
11 
70 
• r )7 
14 
71 
29 
11 
06 
.08 
.05 
.25 
100. 18 
C. 
62.64 
17.82 
3.91 
.31 
.47 
3.22 
4.47 
4.99 
.58 
.65 
.59 
.25 
.08 
.04 
.07 
.28 
100. 37 
57.48 
18. 02 
5.73 
.73 
.04 
.02 
trace 
.12 
.20 
.16 
).96 
52.97 
18.31 
1.86 
6.73 
3.04 
6.51 
3.74 
3.35 
.44 
.31 
1.04 
.81 
.05 
.09 
.14 
.18 
99.57 
48.76 
15.89 
6.04 
4.56 
5.98 
8.15 
3.43 
2.93 
.40 
1.48 
1.65 
.60 
none 
.13 
.06 
.17 
100.23 
