IGNEOUS AND CRYSTALLINE ROCKS. 1038 
X. Granitic gneiss. Contains albite, orthoclase, quartz, and biotite. 
Y. Mica schist. Contains quartz, sillimanite, muscovite, and magnetite. Descrip- 
tions of X and Y supplied by W. Lindgren. Analyses by Schaller, record No. 2163. 
n 
8 
ba 
aa 
Wi. xX. Y. 
@ Loss on ignition. 
.MISCELLANEOUS ROCKS. 
Analyses, elsewhere unpublished, except when otherwise stated, by W. F. Hille- 
brand, record Nos. 1448, 1453, and 1669. Petrographic data supplied by Whitman 
Cross. Names marked with a query are provisional designations only. 
A. Rhyolite, near Robbins’s ranch. Toscanose. Has scattered phenocrysts of 
alkali feldspar, oligoclase, and biotite in a predominant trachytic groundmass of 
alkali feldspar, tridymite, particles of residual glass, and ferritic flakes and grains. 
P.R. C. 1326. 
B. Trachyte (?), Wicher Mountain. Toscanose. Shows biotite and a few glassy 
feldspars in a groundmass resembling that of A. P. R. C. 1328. 
C. Quartz latite, Bare Hills. Pulaskose. Composed mainly of plagioclase and 
alkali feldspar, with small augites and much ferritic matter. Minute prisms of a 
yellowish-brown amphibole (?) and scales of tridymite are also visible. P. R. C. 1327. 
D. Pyroxene latite, Wicher Mountain. Vonzonose. Contains phenocrysts of 
plagioclase, a few of augite, minute specks of iddingsite, and flakes of limonite. In 
the groundmass are plagioclase, orthoclase (?), augite, iddingsite, and hypersthene. 
In the pores tridymite appears. P. R. C. 1325. 
E. Plagioclase basalt, mesa east of Mac Gulch. .dndose. Contains plagioclase, 
augite, olivine, iddingsite, magnetite, biotite, and apatite. P. R. C. 1824. 
F. Plagioclase basalt, Saddle Mountain. Andose. Phenocrysts of augite and 
olivine in a groundmass of plagioclase, orthoclase, augite, magnetite, biotite, and 
apatite. Very fresh. See Cross, Jour. Geology, vol. 5, p. 684. P. R. C. 1828. 
