ARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
173 
5. LEADVILLE REGION. 
Rocks described by Cross in Mon. XII, Appendix A. Analyses 
made in the Denver laboratory. 
A. Porphyry, Mount Zion. Toscanose. Contains orthoclase, 
plagioclase, quartz, biotite, apatite, magnetite, and zircon. Analysis 
by L. G. Eakins. P. R. C. 504. 
B. White, or Leadville, porphyry. Riesenose. Contains ortho- 
clase, plagioclase, quartz, muscovite, magnetite, apatite, and zircon, 
with crystals which appear to be rutile and anatase. Sp. gr., 2.680, 
16°. Analysis by W. F. Hillebrand. P. R. C. 587. 
C. Porphyry, summit of Mount Lincoln. Lassenose. Contains 
quartz, orthoclase, plagioclase, biotite, apatite, sphene, magnetite, 
zircon, and allanite. The sample analyzed showed some muscovite, 
chlorite, and calcite. Sp. gr., 2.670, 16°. Analysis by W. F. Hille- 
•brand. P. R. C. 505. 
Si0 2 .. 
A1A- 
Fe 2 3 - 
FeO.. 
MgO . 
CaO.. 
Na,0. 
K 2 0.. 
H 2 0.. 
Ti0 2 . 
PA- 
MnO. 
SrO .. 
BaO.. 
Li 2 0. 
co 2 . . 
-CI.... 
73.50 
14.87 
.95 
.42 
.29 
2.14 
3.46 
3.56 
.90 
none 
.03 
trace 
100. 12 
B. 
70.74 
14.68 
.69 
.58 
.28 
4.12 
2.29 
2.59 
2.09 
.06 
trace 
.03 
2.14 
trace 
100. 29 
66.45 
15.84 
2. 59 
•1.43 
1.21 
2.90 
3.92 
2.89 
.84 
.10 
.36 
.09 
.07 
trace 
1.35 
.05 
100. 09 
