98 ANALYSES OF ROCKS AND MINERALS, 1880-1908, 
COLORADO. 
1. DENVER BASIN. 
Rocks described by Cross in Mon. XXVII. Analyses A, B, D, and E by L. G. 
Eakins, C by W. F. Hillebrand. All but A were made in the Denver laboratory. 
A. Dolerite, dike near Valmont. Shoshonose. Contains augite, plagioclase, olivine, 
orthoclase, and biotite, with accessory magnetite and apatite. Record No. 1145. 
P.R. C. 534. 
B. Augite separated from A. P. R. C. 105. 
C. Basalt, Table Mountain, lower capping sheet. Shoshonose. Contains plagioclase, 
orthoclase, augite, magnetite, and apatite, with olivine much serpentinized. Sp. gr., 
2.00% 22.0 
D. Basalt, earlier flow, south slope of North Table Mountain. Shoshonose. Contains 
augite, olivine, plagioclase, probably orthoclase, magnetite, apatite, and a little bio- 
tite. P. R. C. 535. 
E. Augite-mica syenite, from north fork of Turkey Creek, Jefferson County. Sho- 
shonose. Contains orthoclase, augite, biotite, rhombic pyroxene, hornblende, plagio- 
clase, quartz, apatite, and magnetite. Sp. gr., 2.857, 29.5°. P. R. C. 532, 
The following rocks from the Denver Basin were analyzed by L. G. Eakins in the 
Denver laboratory, but the analyses do not appear in the monograph. The subjoined 
data have been supplied by Whitman Cross. 
A. Enstatite diabase porphyry, Mount-Morrison. Bandose. Contains labradorite 
and enstatite in a groundmass of considerable amount, which is colorless and crypto. 
crystalline, probably feldspathic, and carries magnetite and other indistinct ferritic 
matter. P. R. C. 533. 
B. Augite andesite, Table Mountain. J. 5.3.3. Contains plagioclase (andesine), 
with rare augite and biotite, in a groundmass of plagioclase, augite, magnetite, and 
minor accessories. This rock contained ptilolite in its vesicular equivalent. De- 
scribed in Proc. Colorado Sci. Soc., 1886, p. 72. 
C. Augite andesite, a pebble from the Denver beds, Table Mountain. Yellow- 
stonose. A few augite and andesite phenocrysts in a groundmass of oligoclase, ortho- 
clase, and quartz (?) grains, with some augite and magnetite. 
