CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
147 
3. SILVER CLIFF AND ROSITA. 
Rocks described by Cross, mostly in 17th Ann.. Part If, p. 263. 
Also, partly, in Proc. Colorado Scientific Soc, vol. 2, p. 228. Analy- 
ses by L. G. Eakins. Those with record numbers attached were made 
in the Washington laboratory: all others in the laboratory at Denver. 
A. Peridotite, Cottonwood Gulch. Contains hornblende, biotite, 
hypersthene, olivine, a little plagioclase, apatite, pyrrhotite, and silli- 
manite(?). P. R. C. 519. 
B. Augite-diorite, Mount Fan-view, Rosita Hills. Contains ajigite, 
biotite, labradorite, and accessory orthoclase, .olivine, magnetite and 
apatite. Sp. gr. 2.870, 32°. Olivine a subordinate constituent 
P. R. C. 526. 
C. The same as B, but with orthoclase in much larger amount. Sp. 
gr. 2.768, U°. Record No., 1091. P. R. C. 529. 
^ D. Trachyte, Game Ridge. Contains sanidine, plagioclase, a little 
biotite, magnetite, apatite, and zircon in a groundmass of orthoclase, 
with a little quartz. Sp. gr., 2.592, 29°. P. R. C. 524. 
E. Trachyte, dark-colored dike. Contains more magnetite than D, 
but otherwise the two are practically identical. Sp. gr. 2.621 24°. 
A. 
Si0 2 . 
A1 2 3 
FeO. 
MgO 
CaO. 
Xa 2 
K 2 0. 
H 2 0. 
Ti 2 0. 
P 2 5 . 
MnO. 
CO,.. 
01.... 
46.03 
9.27 
2. 72 
9.94 
25.04 
3.53 
1.48 
.87 
.64 
B. 
.17 
.40 
50.47 
18.73 
4.19 
4.92 
3.48 
8.82 
4.62 
3.56 
.58 
.51 
.10 
.11 
trace 
trace 
100. 09 
100. 09 
53.80 
20.13 
3.57 
2.63 
2.26 
5.60 
5.20 
4.49 
.90 
.43 
.56 
.29 
66.03 
18.49 
2.18 
. 22 
.39 
.96 
5.22 
5.86 
.85 
.04 
trace 
trace 
65. 41 
18.78 
.94 
.72 
.16 
1.58 
5.91 
5.41 
1.38 
trace 
trace 
99.86 
100. 24 
100. 29 
