182 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY 
[>•'< 
J. Porphyritic lamprophyre, allied to camptonite, Indian Trail 
Ridge, La Plata quadrangle. Oamptonose. Contains phenocrysts of 
oreen hornblende and colorless diopside in a subordinate groundmass 
of plagioclase, orthoclase (?), augite, magnetite, and apatite. Much 
secondary caleite and some serpentine. Analysis by W. F. Hillebrand, 
record No. 1640. Sp. gr., 2.912, 19.5°. P. R. C. 1288. 
K. Lamprophyre, allied to camptonite, Black Face, Telluride quad- 
rangle. Andose. Consists of a fine felt of plagioclase, augite, and 
brown hornblende microliter, with flakes of biotite, and a crypto- 
erystalline part, which is probably in large degree orthoclase. Some 
magnetite and apatite. Analysis by Hillebrand, record No. 1719. Sp. 
gr.', 2.783, 22°. P. R, C. 1282. 
L. Quartz monzonite, northeast of San Miguel Peak, Telluride quad- 
rangle. Toscanose. Contains orthoclase and plagioclase in about 
equal amounts, with abundant quartz and much less augite, horn, 
blende, biotite, magnetite, and apatite. Anatysis hj H. N. Stokes, 
record No. 1761. Sp. gr., 2.720, 34°. Described by Cross in 21st 
Ann., part 2. P. R. C. 1279. 
M. Gabbroitic facies of a diorite-monzonite stock, Ophir Needles, 
Telluride quadrangle. Tonalose. Contains abundant labradorite, with 
augite, hypersthene, biotite, orthoclase, magnetite, apatite, and a very 
little quartz. Analysis by Stokes, record No. 1764. Sp. gr., 2.860, 33°. 
N. Gabbro-porphyry, pass south of Mount Snetfels, Telluride quad- 
rangle. Andose. Contains numerous phenocrysts of labradorite or 
bytownite, in a groundmass of plagioclase, orthoclase (?), augite, 
hypersthene, biotite, magnetite, and apatite. Analysis by Stokes, 
record No. 1764. Sp. gr., 2.949, 26.5°. P. R. C. 1280. 
O. Rhyolite vitrophyre, ridge east of Wind}^ Gap, Telluride quad- 
rangle. Yclloinstonose-lassenose. P. R. C. 1281. Analysis by H. N. 
Stokes. 
j. 
K. 
L. 
M. 
N. 
0. 
Si0 2 
43.98 
13. 30 
3.67 
6.92 
7.03 
10.66 
2.15 
1.64 
.42 
1.52 
1.18 
.32 
.22 
.03 
.05 
.06 
trace 
6.46 
55. 65 
17.04 
2.81 
5.17 
3.42 
6.82 
3.27 
. 2.29 
.46 
1.49 
.90 
.37 
• 20 
none 
.05 
.08 
trace 
none 
65.70 
15. 31 
2.54 
1.62 
1.62 
2. 56 
3.62 
4.62 
.17 
.42 
.72 
.33 
trace 
56.93 
17.03 
3.67 
4.54 
3.30 
6.51 
3.19 
2.58 
.13 
.45 
1.03 
.44 
.10 
47.32 
16.71 
6.92 
5.94 
5.69 
8.51 
2.70 
2.02 
.24 
1.04 
1.50 
.96 
.08 
64 72 
Al,( )., . 
14 18 
Fe 2 0, 
1 58 
FeO 
40 
MgO 
50 
CaO 
Na 2 
2.62 
3 88 
K 2 
1 82 
II 2 Oat 110° 
2 68 
H.,0 above 110°... 
6 82 
Ti0 2 
43 
p 2 o 5 
08 
MnO 
NiO, CoO 
SrO 
.03 
.12 
trace 
none 
.12 
.03 
.06 
.08 
none 
none 
none 
trace 
.06 
.07 
trace 
none 
.19 
trace 
.21 
28 
BaO 
Li 2 
none 
C0 2 
SO, 
CI 

FeS 2 ... 
.54 
- - y- 
100.15 
100.02 
99.53 
100.04 
99. 95 
100. 20 
