158 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [bull. 168. 
The following rocks were also analyzed in the Denver laboratory, 
but the analyses are hitherto unpublished. Petrographic data furnished 
by Whitman Cross. 
A. Granite-prophyry, McNulty Gulch. Contains phenocrysts of 
orthoclase, oligoclase, andesine, quartz, biotite, and altered hornblende, 
in a groundmass of quartz, orthoclase, and magnetite. Accessory 
sphene, allanite, apatite, and zircon, and a little secondary chlorite are 
also present. Analysis by W. F. Hillebrand. P. R. C. 586. 
B. Granite- porphyry, Jefferson tunnel. Contains orthoclase, oligo- 
clase, quartz, and biotite, in a groundmass of mainly quartz and ortho- 
clase; also accessor}^ magnetite, apatite, zircon, and allanite. Chlo- 
rite appears as a decomposition product of biotite, and calcite and 
magnetite are present in small amounts. Analysis by Hillebrand. 
C. Same as B. Analysis by L. G. Eakins. P. R. C. 583. 
D. Diorite -porphyry, Copper Mountain. Contains oligoclase, horn- 
blende, and biotite, in a groundmass of quartz, orthoclase, plagioclase, 
and magnetite; also accessory zircon, sphene, and apatite, and a little 
secondary chlorite and epidote. Analysis by Eakins. P. R. C. 585. 
E. Diorite-porphyry, McNulty type. Contains oligoclase, andesine, 
hornblende, biotite, and magnetite, in a groundmass of orthoclase, pla- 
gioclase, quartz, magnetite, apatite, allanite, and sphene; also second- 
ary chlorite, epidote, and calcite. Analysis by Eakins. P. R. C. 584. 
A. 
B. 
C. 
D. 
E. 
Si0 2 
68.60 
16.21 
1.67 
1.57 
1.05 
2.61 
3.29 
3.88 
.92 
.21 
.09 
trace 
65.94 
16.00 
.60 
1.74 
1.02 
2.87 
3.85 
4.56 
1.13 
.23 
.14 
trace 
65.51 
17.01 
none 
2.79 
.90 
3.16 
3.82 
4.67 
1.78 
.13 
67. 01 
18.03 
.66 
.72 
.84 
3.99 
4.42 
3.53 
.91 
.10 
.09 
63.02 
17.61 
1.78 
2.76 
1.63 
3.30 
4.72 
3.23 
2.03 
.16 
trace 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 
P„0, 
MnO 
SrO .. 
BaO 
.10 
.08 
C0 2 
.19 
.03 
1.55 
.03 
CI 
trace 
.38 
s 
FeS 2 
.60 
Sp-gr 
• 
100. 32 
2. 640, 27° 
100. 26 
2. 672, 21° 
100. 15 
2. 666, 26° 
100. 40 
100. 32 
2.689, 16°5 
