,ARKE.] 
IGNEOUS AND CRYSTALLINE HOCKS. 
1L )( .) 
5. CASTLE MOUNTAIN DISTRICT. 
Rocks described by Weed and Pirsson in Bull. 139. Analyses made 
y Pirsson in the laboratory of the Sheffield Scientific School. 
A. Rhyolite, between Fourmile and Fivemile creeks, near Smith 
liver. Contains quartz, soda orthoclase, tourmaline, and a little iron 
iv and zircon. P. R. C. 560. 
B. Quartz-tourmaline-porphyry, upper Fourmile Creek. Contains 
uartz, orthoclase, plagioclase, tourmaline, fluorite, and a little white 
lica, apatite, and zircon. P. R. C. 558. 
C. Granite, Elk Peak. Contains quartz, orthoclase, oligoclase, I no- 
te, hornblende, iron ore, apatite, sphene, and zircon. The last three 
linerals are rare. P. R. C. 551. 
D. Quartz-porphyry, sheet on ridge between Fourmile and Checker- 
oard creeks. Contains quartz, plagioclase, an untwinned feldspar 
ad biotite, with occasional grains of iron ore and crystals of apatite 
nd zircon. P. R. C. 557. 
E. Rhyolite-pitchstone, forks of Checkerboard Creek. Essentially 
lass, inclosing grains of iron ore. P. R. C. 561. 
F. Aplitic granite, dike between Blackhawk and Robinson. Con- 
lins quartz and unstriated feldspar, some plagioclase, and occasional 
iotite. P. R. C. 553. 
G. Quartz-porphyry, Musselshell Canyon. Contains quartz, biotite, 
lagioclase, apatite, iron ore, and zircon. P. R. C. 556. 
A. 
B. 
c. 
D. 
E. 
F. 
G. 
Si0 2 
74.90 
13.64 
.66 
.50 
trace 
.61 
4.22 
4.64 
.33 
.15 
trace 
trace 
74.82 
13.80 
.37 
.30 
.10 
.17 
4.33 
4.81 
.83 
.25 
trace 
trace 
72.48 
13.14 
1.66 
1.02 
.15 
1.04 
4.22 
4.88 
.42 
.32 
trace 
trace 
72.38 
14.71 
1.09 
.82 
.70 
.67 
4.28 
4.15 
.92 
.10 
trace 
trace 
72.56 
12.33 
.80 
.82 
trace 
trace 
5.36 
3.08 
4.59 
.20 
trace 
72.88 
12.90 
.74 
1.05 
.75 
.81 
3.72 
5.03 
1.22 
.45 
.05 
71.67 
15. 82 
1.18 
.35 
.13 
.25 
4.46 
4.45 
1.21 
.10 
trace 
ALA 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 
Ti0 2 
MnO 
Li 2 
Sp.gr 
99.65 
2.61 
99.78 
2.59 
99.33 
2.62 
99.82 
2.61 
99.74 
2.37 
99.60 
2.64 
99.62 
2.60 
Bull. 168- 
