70 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[no. 228. 
ARKANSAS. 
99. 84 
Ouachitite, dike near Maple Spring, 1 miles southwest of Hot 
Springs. SB. 2 of etmdase. Described by Kemp, in Ann. Rep. Geol. 
Survey Arkansas, 1890, vol. 2, p. 399. A dike rock of the monchi- 
quite group. Contains abundant and conspicuous augite and biotite, 
magnetite, and minor accessory minerals in a groundmass, considered 
by Kemp as glass. Calcite and other secondary products are also 
present. According to Pirsson, Journ. Geol., vol. 4, p. 679, the so- 
called "glass" in the monchiquites is really analcite. Analysis by 
L. G. Eakins, record No. 1023. P. R. C. 395. 
SiO, 36. 40 
A1 2 3 12.94 
Fe 2 3 S. 27 
FeO 4.59 
MgO 11.44 
CaO 14.46 
N^O 97 
TEXAS. 
A. Quartz-pan tellerite, Vieja Mountains, San Carlos, Presidio 
County. Liparose. Description furnished by E. C. E. Lord. Con- 
tains anorthoclase, augite, and grains of quartz in a groundmass of 
gegirine augite, a brown hornblende which is probably barkevikite, 
orthoclase, and quartz. Magnetite and apatite are present as accessory 
minerals. AnaWsis by George Steiger, record No. 1581. 
The following rocks from Uvalde County were collected by T. Way- 
land Vaughan. Petrographic data furnished by Whitman Cross. 
Analyses by W. F. Hillebrand, record No. 1681. 
B. Plagioclase-basalt, Pinto Mountain, Brackett quadrangle. Lim- 
hurgose. Contains olivine, augite, plagioclase (labradorite), biotite, 
a very little alkali feldspar ('( ), magnetite, and apatite. Sp. gr., 3.118, 
20°. P. R. C. 1067. 
C. Basanite, Mount Inge, Uvalde quadrangle. Lujavrose. Contains 
sanidine, nephelite, hornblende, augite, tegirine-augite, olivine, mag- 
netite, apatite, and a trace of pyrite. Sp. gr. , 2. 770, 20°. P. R. C. 1069. 
