KAWICH RANGE, IGNEOUS ROCKS. 
lava was very viscous. Biotite is fairly abundant in some slide- 
while in others it is represented by ill-defined pseudomorphs. 
Quartz latites are widely interbedded with the rhyolites, being par- 
ticularly well exposed at Stinking Spring. They are characterized 
in the hand specimen by the presence of phenocrysts of both striated 
and unstriated feldspar and a hornblende-like mineral which, reaches 
a maximum length of one-fourth inch. Microscopic examination, 
shows a glassy groundmass containing as phenocrysts quartz, ortho- 
clase, plagioclase, and hornblende or augite. Both feldspars are 
often zonally built. Magnetite and apatite are common accessories. 
Brown glassy dacites are less widely distributed. Microscopic 
examination shows a rock similar to the quartz latite, except that 
plagioclase is present to the almost total exclusion of orthoclase, and 
ilmenite accompanies magnetite. 
Many beds of the acidic series are flow breccias, including angular 
fragments of texturallv similar or dissimilar acidic rocks, indicating 
that portions of the flow solidified prior to the cessation of movement 
in other parts. White, slightly porous pieces of rhyolitic glass. 
elongated in the direction of flow, are common in certain areas. Sim 
ilar inclusions characterize the earlier rhyolite of Goldfield and the 
rhyolite of Bullfrog. 
About H miles east of Rose Spring is an area of consolidated white 
shaly sandstones and coarse, well-bedded sandstones. The micro- 
scope shows that the rock is a typical tuffaceous sandstone of rhyo- 
litic composition. It was probably deposited in a small body of water 
[contemporaneous with the outflow of the earlier rhyolite. 
The acidic series imparts to the Kawich Range a white, yellow 7 , or 
(red color, and in places all these are distributed in broad bands 
'either horizontally or slightly tilted. Spires are developed on canyon 
Walls in jointed rhyolite, the same rock forming rounded bosses in the 
broader, more mature valleys. South of the detrital gap in the range 
the hills have a marked northwest-southeast alignment parallel to the 
strike of resistant rhyolite flow bands. 
The earlier rhyolite of the Kawich Range lies below supposed Sie- 
jbert lake beds and is similar to and probably contemporaneous with 
jthe rhyolite of the Belted, Cactus, and Reveille ranges and the Bull- 
frog Hills. In a general way the series is comparable with the pre- 
Biebert rhyolites and dacites of the Tonopah district," which are 
probably of early Miocene age. 
Earlier basalt. — Minor flows of basalt were extruded contempo- 
raneously with the earlier rhyolite. The small mass of dense black 
msalt with sparse, medium-sized, glassy feldspar phenocrysts three- 
fourths of a mile east of Silverbow is probably such flow 7 . This 
rock on microscopic examination proves to be a noncrystalline 
° Spun-, J. E., Prof. Paper U. S. Geol. Survey No. 42, 1905, pp. .37-43. 
