148 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
F. Andesite, Pringle Hill. Contains plagioclase, orthoclase, quartz, 
biotite, augite, magnetite, and apatite, with sometimes a little horn- 
blende. Sp. gr. 2.651, 17.8°. Record No. 1124. P. R. C. 528. 
G. Pringle andesite, dike. Like F, but often contains sphene. Sp. 
gr. 2.690, 28°. P. R. C. 527. 
H. Bunker andesite, Lookout Mountain. Contains plagioclase, 
orthoclase, augite, biotite, hornblende, quartz, magnetite, and apatite. 
Sp. gr. 2.699, 34°. Record No. 1091. 
J. Altered Bunker andesite, Robinson Plateau. Biotite gone, mag- 
netite altered to limonite, feldspars not much attacked. Record No. 
1124. Sp. gr. 2.580, 19.7°. 
J. Much-decomposed Bunker andesite, ridge near Knickerbocker 
Hill. Augite, hornblende, and biotite all replaced by decomposition 
products, plagioclase much muscovitized. Record No. 1124. P. R. C. 
592. 
F. 
G. 
H. 
I. 
J. 
Si0 2 
58.94 
17.19 
2.63 
1.98 
1.52 
4.45 
4.20 
3.90 
4.53 
.27 
.23 
.10 
63.49 
18.40 
2.44 
1.09 
.66 
2.30 
5.70 
4.62 
1.04 
trace 
trace 
.16 
trace 
57.01 
18.41 
3.69 
2.36 
2.34 
4.29 
4.95 
3.72 
2.29 
.27 
.42 
.21 
63.88 
19.96 
2.21 
.57 
.58 
2.03 
4.19 
3.88 
2.63 
67.13 
18.41 
.45 
.07 
.44 
.55 
4.17 
5.28 
2.98 
.30 
trace 
trace 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 
Ti0 2 .. 
P 9 (\ 
MnO 
trace 
co 2 
99.94 
99.90 
99.96 
99.93 
99.78 
