CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
151 
U. Syenite, Silver Cliil'. Contains orthoclase and plagioclase in 
nearly equal amounts, colored by ferric hydroxide, with amphibole, a 
little biotite, and secondary epidote, calcite, and chlorite. Sp. gr. 
2.689, 20°. P. R, C. 520. 
V. Quartz-alunite rock, Democrat Hill. About two-thirds quartz 
and one-third alunite. Record No. 1126. P. R. C. 596. 
W. The same, Mount Robinson. About one-fourth alunite. Record 
No. 1248. P. R. C. 593. 
X. Quartz-diaspore rock, Mount Robinson. About 18 per cent 
diaspore, the rest quartz. Record No. 1167. P. R. C. 594. 
Rocks V, W, and X are also described in Amer. Journ. Sci., 3d 
series, vol. 41, p. 471. These three rocks are decomposition products 
of rhyolite. 
u. 
V. 
W. 
X. 
Si0 2 
59.78 
16.86 
3.08 
3.72 
.69 
2.96 
5.39 
5.01 
1.58 
65. 94 
12.95 
.33 
.07 
.05 
.10 
1.19 
2.32 
4.47 
69.67 
13.72 
76.- 22 
19.45 
trace 
A1 2 3 
Fe.,Oo 
FeO . . 
MgO 
trace 
.07 
.34 
2.44 
4.73 
CaO 
trace 
trace 
trace 
3.82 
.11 
.13 

Na 2 
K 2 
H 2 
Ti0 2 
P.,0. 
MnO 
.14 
trace 
trace 
12. 47 
BaO 
so 3 
9.27 
.29 
co 2 
.75 
99.96 
99.89 
100. 24 
100. 02 
