118 ANALYSES OF ROCKS AND MINERALS, 1880-1908. 
. Nepheline tephrite, Elkhead Mountain, Routt County. Undescribed. Sp. 
gr., 2.888, 12.2°. 
X. Portion of N soluble in hydrochloric acid. Recalculated to 100 per cent, 39.95 
per cent of the entire rock. Analyses W, X, made by L. G. Eakins in the Denver 
laboratory. 
Y. Olivine basalt, Pilot Knob, Routt County. Collected by H. S. Gale, who fur- 
nishes the description. Contains plagioclase, olivine, augite, magnetite, apatite, and 
possibly other accessory minerals. Analysis by W. F. Hillebrand, record No. 2235. 
100.26 | 100.00 | 100.23 
UTAH. 
1. ROCKS FROM THE TINTIC DISTRICT. 
Described by Tower and Smith in 19th Ann., pt. 3, pp. 609 et seq. Analyses by 
Stokes, record No. 1746. 
A. Gray, porphyritic rhyolite, south of Pinyon Creek. Toscanose. Contains 
phenocrysts of sanidine, quartz, biotite, plagioclase, and hornblende; the last min- 
eral sparingly. Also tridymite, magnetite, apatite, zircon, and a small amount of 
glassy residue. P. R. ©. 1039. 
B. Quartz porphyry, Swanseamine. Toscanose. Phenocrysts of feldspar and quartz, 
the orthoclase somewhat altered. Microscopic biotite occurs sparingly. Also contains 
magnetite, apatite, zircon, a little chlorite, and secondary pyrite. P. R. C. 1040. 
