192 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [no. 228. 
5. MISCELLANEOUS ROCKS. 
A. Rhyolite, Thomas Range. Toscanose. Analysis made by L. G. 
Eakins in the Denver laboratory. Described by Cross in Proe. Colo. 
Sci. Soc, vol. 2, p. 69. Contains phenocrysts of quartz and sanidine 
in a groundmass mainly made up of quartz and alkali feldspar. 
B. Rhyolitic glass or pitchstone, edge of Gold Mountain mining dis- 
trict, 8 miles north of west from Marysvale. Liparose. Identified by 
Whitman Cross, but not published. Sp. gr., 2.25 at 23.5°. Analysis 
by W. F. Hillebrand, record No. 1833. 
Si0 2 . 
ALA 
Fe 2 3 
FeO . 
MgO. 
CaO . 
Na 2 
K 2 0. 
H 2 0. 
Ti0 2 . 
MnO 
Li 2 0. 
74.49 
14.51 
.57 
.32 
trace 
1.03 
3.79 
4.64 
.64 
trace 
trace 
99. 99 
70.17 
11.83 
.93 
none 
.06 
.76 
3.85 
3.74 
8.72 
.17 
100.23 
