126 ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [bull. 168 
G. Syenite-porphyry, intrusive sheet, between Yogo Peak and Big 
Baldy Mountain. Abundant phenocrysts of hornblende and ortho- 
clase, with less biotite and plagioclase, in a groundmass of alkali feld 
spar with accessory quartz. Also contains iron ore and apatite, with 
secondary calcite, chlorite, sericite, and kaolin. Analysis b}^ Hille- 
brand. 
H. Granite-syenite-porphyry, north end of Thunder Mountain. 
Phenocrysts of orthoclase, oligoclase, hornblende, and biotite, in a 
groundmass of alkali feldspar and very abundant quartz. Also con- 
tains a little sphene, iron ore, and apatite, very little secondary 
chlorite and limonite, and a trace of kaolin. Analysis by Stokes. 
I. Quartz-syenite-porphyry, top of Big Baldy Mountain. Pheno- 
crysts of orthoclase, plagioclase, biotite, iron ore, brown hornblende, 
and sphene, in a groundmass of quartz and alkali feldspar. Also con- 
tains a little apatite, with traces of chlorite, limonite, and kaolin. 
Analysis by HillebrancL 
J. Syenite-diorite-porphyry, talus slope on west side of Bear Park. 
Phenocrysts of biotite, hornblende, plagioclase, and orthoclase, in a 
groundmass of quartz and alkali feldspar. Also contains a little mag- 
netite, chlorite, white mica, and apatite. Analysis by Stokes. 
K. Diorite-porphyry, Steamboat Mountain. Phenocrysts of ortho- 
clase, plagioclase, hornblende, and biotite, with a little iron ore and 
apatite, in a groundmass of orthoclase, plagioclase, and quartz. Anal- 
ysis by Stokes. 
L. Diorite, Carpenter Creek, near Neihart. Contains green horn- 
blende, biotite, and plagioclase, with some apatite, iron ore, calcite, 
kaolin, and muscovite, and a very little quartz and orthoclase. Analysis 
by Hillebrand. 
