IGNEOUS AND CRYSTALLINE ROCKS. 
171 
The following" analyses, all by L. G. Eakins, do not appear in the 
published memoir just cited. A and B were made in the Denver lab- 
oratory. The petrographic details have been supplied by Whitman 
Cross. 
A. Spherulitc in rhyolite, ridge west of Mount Tyndall. Mainly 
composed of quartz and feldspar needles, with some ferritic coloring 
due to decomposition of trichites. P. R. 0. 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°. 
The spherulites, C, D, E, F, and G, are made up of orthoclase 
needles, with free silica in fibers or grains, or rarely as tridymite. 
The " soluble silica" is that which is dissolved by sodium carbonate 
solution. 
A. 
B. 
C. 
D. 
E. 
F. 
G. 
H. 
Si0 2 
71.27 
16.02 
1.41 
.17 
trace 
.35 
5.76 
4.08 
1.14 
trace 
trace 
85.50 
7.42 
1.23 
.34 
.82 
.37 
.74 
2.64 
1.22 
none 
.08 
74.47 
13.87 
80.61 
10.94 
83.91 
9.54 
79.21 
12.24 
78.77 
12. 46 
78.74 
A1A 
Fe 2 3 
12.01 
trace 
FeO 
MgO 
CaO 
trace 
.51 
2.10 
7.46 
1.88 
.09 
.26 
2.90 
3.02 
2.20 
trace 
.19 
.62 
5. 06 
.69 
.11 
.43 
2.58 
5.26 
.66 
.09 
.34 
2.12 
5.84 
.70 
.09 
.16 
Na,0 
K 2 
2.21 
5.84 
H 2 
PA 
MnO 
.92 
.13 
Soluble Si0 2 .. 
100. 20 
100. 36 
100. 29 
12.72 
100. 02 
11.12 
100. 01 
1.06 
100. 49 
1.27 
100. 32 
1.25 
100. 10 
