IGNEOUS AND CRYSTALLINE ROCKS. 107 
W. Quartz-alunite rock, Democrat Hill. About two-thirds quartz and one-third 
uunite. Record No. 1126. P. R. C. 596. 
X. The same, Mount Robinson. About one-fourth alunite. Record No. 1248. 
P.C. R. 593. 
Y. Quartz-diaspore rock, Mount Robinson. About 18 per éent diaspore, the rest 
quartz. Record No. 1167. P.R. C. 594. 
Rocks W, X, and Y are also described in Am. Jour. Sci., 3d ser., vol. 41, p. 471. 
These three rocks are decomposition products of rhyolite. 
The following analyses, all by L. G. Eakins, do not appear in the published memoir 
ust cited. .A and B were made in the Denver laboratory. The petrographic details 
ave been supplied by Whitman Cross. 
A. Spherulite in rhyolite, ridge west of Mount Tyndall. Mainly composed of 
juartz and feldspar needles, with some ferritic coloring due to decomposition of 
Tichites. P.R. C. 1077. 
B. Rhyolitic residual glass, same locality as A. P. R. C. 1077. 
C. Interspherulitic mass, Rosita. Record No. 1285. 
D. Spherulite, Rosita. Record No. 1286. 
E, F, G. Spherulites, Silver Cliff. Record Nos. 1285, 1286. 
H. Spherulite of rhyolite, Fleetwood tunnel, Silver Cliff. Sp. gr., 2.389, 20° 
>. R. C. 1075. 
The spherulites, (, D, E, F, and G, are made up of orthoclase needles, with free 
ilica in fibers or grains, or rarely as tridymite. 
The ‘‘soluble silica” is that which is dissolved by sodium carbonate solution. 
