168 
ANALYSES OF ROCKS, IT. S. GEOLOGICAL SURVEY. [no. 228. 
K. Dacite, Bald Mountain, near Rosita. Lassenose. Contains pla- 
gioclase, biotite, hornblende, sometimes augite, magnetite, and quartz. 
Sp. gr., 2. 574, 21°. Record No. 1068. P. R. C. 530. 
L. Mica-dacite. Lassenose. Contains plagioclase, sanidine, biotite, 
and quartz. Sp. gr., 2.563, 21°. Record No. 1068. 
M. Rhyolite, Pennsylvania Hill. Toscanose. Sp. gr., 2.470, 26°. 
Record No. 1079. P. R. C. 525. 
N. Rhyolite, Round Mountain. Omeose. Contains sanidine, quartz, 
some glass, and accessory garnet. P. R. C. 521. 
O. Rhyolite, Silver Cliff Magdeburgose. Sp. gr., 2.560, 15°. 
Record No. 1125. P. R. C. 522. 
Si0 2 . 
FeA 
FeO. 
MgO 
CaO. 
Na 2 
H 2 0. 
Ti0 2 . 
PA 
MnO 
66.46 
17.91 
2.42 
.35 
.49 
2.89 
4.79 
3.74 
1.01 
trace 
100. 06 
67.49 
17.76 
2.54 
.08 
.35 
1.67 
5.03 
4.40 
.52 
trace 
trace 
99. 84 
M. 
70.87 
15. 18 
2.18 
.12 
.60 
1.58 
3.47 
5.04 
1.08 
trace 
trace 
trace 
100. 12 
N. 
75.20 
12.96 
.37 
.27 
.12 
.29 
2.02 
8.38 
.58 
trace 
.03 
100. 22 
0. 
75.39 
13.65 
.38 
.18 
.15 
.51 
1.84 
6.81 
1.13 
trace 
trace 
.14 
100. 18 
