IGNEOUS AND CRYSTALLINE ROCKS. 
105 
G. Rhyolite, " Great Paint Pots." Analysis by Gooch, No. 113, 
hitherto unpublished. 
H. Rhyolite, "Elephants Back.' 1 Porphyritic obsidian. Analysis 
by Whitfield, No. 423, hitherto unpublished. Reported by Iddings as 
containing- quartz, sanidine, and a little augite and magnetite, in a 
glassy, microlitic groundmass. 
I. Rhyolite, Mount Sheridan. Composition reported by Iddings as 
quartz and sanidine, with a little magnetite and augite. Analysis by 
Whitfield, No. 426, hitherto unpublished. 
J. Rhyolite, Madison Plateau. Like I. Analysis by Whitfield, No. 
427, not yet published. 
K. Trachytic rhyolite, Elk Creek. Analysis by Whitfield, No. 428, 
hitherto unpublished. Reported by Iddings as containing sanidine, 
labradorite, and little biotite, in a groundmass of quartz and alkali 
feldspar 
Si0 2 .. 
A1A- 
Fe 2 3 
FeO.. 
MgO . 
CaO.. 
Na 2 0. 
K 2 0_. 
H 2 0.. 
Ti0 2 . 
PA ■ 
MnO. 
Li 2 . 
SO, .. 
<:. 
75.71 
11.11 
1.56 
.37 
.08 
.88 
4.64 
4.18 
.35 
1.25 
07 
100. 20 
75.34 
12.51 
.42 
1.55 
.32 
1.07 
3.31 
4.17 
.86 
none 
none 
.07 
trace 
.42 
100. 04 
75.89 
12.27 
1.12 
1.37 
.29 
.86 
3.23 
3.42 
.82 
.50 
none 
none 
.01 
.28 
100. 06 
75. 19 
13.77 
.61 
1.37 
.09 
.68 
3.83 
3.33 
.65 
none 
none 
trace 
.02 
.29 
99.83 
64.65 
17.80 
2.33 
2.10 
.81 
1.73 
4.18 
2.83 
3.06 
trace 
trace 
trace 
.17 
.43 
100. 09 
