CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
J SI 
plagioclase, and quartz. Also secondary epidote, chlorite, and calcite. 
Analysis by Hillebrand, record No. 1636. Sp. gr., 2.677, 21°. A 
trace of sulphur is present. Described by Cross in 21st Ann., part 2. 
P. R. C. 1283. 
G. Syenite, between Tirbircio and Schurman gulches, La Plata 
Mountains. Monzonose. Contains much alkali feldspar, some oligo- 
clase, augite, biotite, and hornblende, with a little titanite, magnetite, 
and apatite. Analysis by H. N. Stokes, record No. 1764. Sp. gr., 
2.701, 25°. P. R. C. 1286. 
H. Augitic monzonite, BabcockPeak, La Plata Mountains. Andose. 
Contains orthoclase and plagioclase in about equal amounts, with 
augite and hornblende, and a little quartz, titanite, magnetite, and 
apatite. Analysis )ry Stokes, record No. 1761. Sp. gr., 2.767, 2»'> . 
Described by Cross in 21st Ann., part 2. P. R. C. 1285. 
1. Porphyritic lamprophyre, allied to camptonite, Snowstorm Peak, 
La Plata Mountains. Kentallenose. Contains numerous phenocrysts 
of green hornblende, augite, and plagioclase, in a groundmass of plagi- 
oclase, orthoclase, augite, magnetite, and apatite. Some secondary 
calcite. Analysis by Hillebrand, record No. 1640. Sp. gr., 2.906, 21°. 
P. R. C. 1287^ 
E. 
G. 
II. 
SiO 
Fe 2 3 
FeO 
MgO 
CaO 
Na./) 
K 2 
H 2 OatllO°... 
H 2 ( ) above 110 c 
Ti0 2 
PA 
VA 
NiO, CoO 
MnO 
Sr() 
BaO 
Li 2 
CO.. 
so 3 
CI 
FeS, 
55. 53 
10.78 
4.06 
3. 35 
3.00 
0. 96 
4. 31 
3. 57 
.09 
.55 
.95 
.47 
.02 
trace 
.16 
.11 
.13 
trace 
.09 
(M 
60.44 
16. 65 
2.31 
3. 09 
2.18 
4.22 
5. 18 
2.71 
. 36 
1.07 
.60 
.29 
.02 
none 
.13 
.11 
.12 
trace 
.48 
59. 79 
1 7. 25 
3.60 
1.5! t 
1.24 
3.77 
5.04 
5. 05 
.19 
.39 
.67 
. 35 
.20 
.11 
.14 
trace 
.72 
.04 
trace 
57. 42 
18. 48 
3.74 
2. 10 
1.71 
6. 84 
4.52 
3. 71 
.08 
.28 
.86 
.36 
.09 
.08 
.15 
trace 
none 
none 
.03 
47. 25 
15.14 
5.05 
-1.1)5 
0. 87 
9. 98 
2. 39 
2.60 
.40 
2. 12 
1. 22 
.25 
.05 
.02 
.17 
. 05 
.08 
trace 
1.87 
100. r 
99.96 
100.14 
LOO. 45 
100.46 
