IGNEOUS AND CRYSTALLINE ROCKS. 59 
The four following rocks from Encampment quadrangle are described by A. C. 
Spencer in P. P. 25. Analyses by E. T. Allen, record No. 2048. 
K. Norite, near head of Cow Creek, about three-fourths of a mile from Bridger 
Peak. Auvergnose. Contains chiefly hypersthene and labradorite, the latter slightly 
altered to sericite. Biotite and magnetite are present, with a few grains of diallage 
and a little hornblende. 
L. Diorite derived from norite, altered form of K. The pyroxene is completely 
changed to uralite and the feldspar is largely decomposed. 
M. Diorite derived from norite, 2 miles west of the Verdi mine. Contains uralite 
and labradorite, with a little biotite and magnetite. 
N. Diorite, probably derived from gabbro, near head of Big Sandstone Creek. 
Contains much zoisite derived from the feldspars. ; 
K. L. M. N. 
The following rocks, from Sundance quadrangle, are described by W. 8. T. Smith 
in Folio 127. Analyses by George Steiger, record No. 1999. 
O. Trachytoid phonolite. Pulaskose. Contains phenocrysts of orthoclase, segirine- 
augite, a little augite, nepheline (?), magnetite, garnet, titanite, andapatite. Ground- 
mass mainly feldspar, probably orthoclase, and other minerals as above, with possibly 
some species of the sodalite group. P. R. C. 1756. 
P. Phonolite. Essexose. Contains phenocrysts of feldspar, apparently orthoclase 
and anorthoclase, egirine-augite or little augite, garnet, probably nosean, titanite, 
magnetite, and apatite. In the groundmass, feldspar (orthoclase ?), egirine-augite, 
and possibly sodalite. P. R. C. 1757. 
Q. Trachytoid phonolite. Akerose-laurvikose. Contains phenocrysts of feldspar 
(orthoclase and plagioclase ?), egirine-augite, magnetite, titanite, and apatite. In 
the groundmass, feldspar, magnetite, egirine-augite, and apatite. P. R. ©. 1758. 
R. Augite vogesite. Kentallenose. Contains phenocrysts of augite, magnetite, 
apatite, biotite, orthoclase, and plagioclase. Same minerals in the groundmass, with 
with perhaps some species of the nepheline-sodalite group. 
