170 
ANALYSES OF ROOKS, U. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
2. MOUNT TAYLOR REGION. 
Rocks received from J. S. Diller. Analyses by T. M. Chatard, rec- 
ord Nos. 219, 227, 228, 235, 271, 268, and 269. Not hitherto pub- 
lished. Petrographic details furnished by Diller. 
A. Lava, canyon on east side of San Mateo Mountain. 
B. Phonolitic andesite, canyon on east side of San Mateo Mountain. 
Contains feldspar and corroded augite, with sometimes olivine, in a 
groundmass of feldspar and a green ferromagnesian silicate. 
C. Mica-andesite, canyon on east side of San Mateo Mountain. 
Shows prominent plagioclase, with augite and biotite. 
D. Mica-andesite, 6 miles northeast of Grant's. Principally plagio- 
clase and biotite, with less epidote, quartz, sphene, and carbonates. 
E. Basalt, 6 miles northeast of Grant's. Contains chiefly plagioclase, 
augite, and olivine, with much magnetite. 
F. Augite from E. 
G. Feldspar from E. Analysis on three-fourths gramme of material. 
