122 ANALYSES OF BOCKS, U, S. GEOLOGICAL SURVEY. 
[NO. 228. 
L. Trachytic rhyolite-tuff, Two Ocean Pass. Analysis by Whitfield, 
No. 906, hitherto unpublished. Reported by Iddings as containing 
sanidine, labradorite, biotite, magnetite, and augite, in a somewhat 
altered, glassy groundmass. Also contains fragments of andesite. 
M. Glassy trachyte, approaching rhyolite, Sunset Peak, Bear Gulch. 
Tosccmose. Contains phenocrysts of sanidine, plagioclase, and biotite. 
See Iddings, Bull. Phil. Soc. Washington, vol. 12, p. 205; also Mon. 
XXXII, Pt. II. Analysis by L. G. Eakins, record No. 1378. 
N. Altered rhyolite, "Iron Pot," Lower Basin. Collected by 
W. H. Weed. Analysis by Whitfield, No. 546, hitherto unpublished. 
O. Dacite-porphyry, Echo Peak. Near alaskose. 
P. Same as O, Mount Holmes. Alsbachose. Analyses O and P by 
Whitfield, Nos. 421, 422, hitherto unpublished. Reported b} r Iddings 
as containing plagioclase, probably oligoclase, quartz, little biotite, 
and magnetite. 
Si0 2 .. 
A1A- 
Fe 2 3 
FeO.. 
MgO. 
CaO.. 
Na 2 0, 
K 2 0.. 
H 2 0.. 
Ti0 2 .. 
PA- 
MnO 
BaO. 
Li 2 0. 
SO... 
61.15 
15.70 
4.31 
1.12 
3.04 
2.84 
1.54 
2.22 
7. 05 
.69 
.75 
trace 
none 
.18 
100. 59 
M. 
69.45 
14.92 
3.16 
.23 
.05 
1.19 
3.19 
5. 95 
1.69 
.19 
.06 
.07 
.03 
100.18 
N. 
89.20 
2.39 
1.21 
none 
trace 
trace 
1.11 
.79 
5. 09 
none 
none 
44 
100. 23 
74.51 
14.83 
1.09 
trace 
.47 
.81 
4.38 
2.72 
.92 
none 
trace 
none 
02 
24 
99.99 
69.54 
17.95 
2.50 
. 22 
.50 
1.80 
4.30 
1.21 
1.96 
none 
none 
none 
trace 
.37 
100. 35 
