170 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
pebbles of these rocks. The later basalt lies upon the eroded surface 
of the rhyolite. This rhyolite is practically continuous with that of 
the Bullfrog Hills and is of similar lithologic character. It is 
roughly to be correlated with the earlier rhyolite of the Kawich, 
Belted, and Reveille ranges, probably of early Miocene age. 
Earlier basalt. — Basalt fragments are locally contained in the 
rhyolite flow breccias, and at several places thin lenses of basalt, too 
small to show on the map. are interbedded with the rhyolite. The 
best example i- at the Happy Hooligan mine, L2 miles south of west 
of Rhyolite. Mr. F. L. Ransome " states that recent mining develop- 
ment has here exposed a basalt bed from 25 to 50 feet thick between 
the rhyolite and the Pogonip limestone. The rhyolite of the Bull- 
frog Hill- and the Kawich Range also contains minor flows of ba- 
salt, a fact further indicating the contemporaneity of the two rocks. 
Later rhyolite mid biotite latite. — To the southeast of the Stainin- 
ger ranch is an area covering about 12 square miles of rhyolites and 
latites interbedded with the Siebert lake beds. The rhyolites are the 
older of these lavas and the latite- the younger. 
The rhyolites are semitranspafenl to opaque, glassy or semiglassy 
lock-, with lVw quartz, feldspar, and biotite phenocrysts. In color 
they range from light gray, through red, to black. Flow breccias are 
common. Perlitic parting, which causes the rock to disintegrate into 
pebble-like masses, is well developed in many of the flows. Flow 
folding, with overturned isoclinals, in places with horizontal axes, 
is not unusual. The spherulites, which are very abundant in some 
flows, making up at least one-third of the rock, are similar to those 
already described from the Mount Jackson hills (p. 67). In some 
cases large spherulites, rudely globular and from 3 inches to 1 foot in 
diameter, inclose smaller ones. The large spherulites are cut by 
horizontal flow lines, while the smaller have the typical radiate struc- 
ture. Lithophysse also occur. 
The latites are white semipumiceous rocks with myriad bronze- 
brown hexagonal plates of mica and less conspicuous phenocrysts of 
feldspar. In some instances the biotite plates have an excellent ori- 
entation in the place of flow and the rock breaks into platy masses 
along the flow banding. A single thin section examined under the 
micro-cope showed the rock to be a biotite latite, with groundmass 
of a vesicular colorless glass. The phenocrysts exceed the ground- 
mass in bulk, and orthoclase and biotite are more abundant than 
plagioclase. Apatite is present as an accessory mineral. 
The later rhyolite is similar lithologically to the rhyolite associ- 
ated with the Siebert lake beds of the Mount Jackson hills, and the 
two series are probably approximately contemporaneous. In the 
" Oral communication. 
