96 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
have occurred. To the north of Alkali Spring some quartz veins cut 
iron-stained kaolinized and silicified rhyolite. Prospectors report 
that the quartz carries low-grade values. 
Over a considerable area south of the Goldfield-Cactus Spring- 
road, beneath the north end of the andesite How, which caps the high 
mountain south of the median line, and in several smaller areas the 
rhyolite has been silicified and kaolinized. (See fig. 4. p. 43.) Quartz 
veinlets occur in some of these areas. Masses of hematite and limon- 
ite outcropping 2 miles S. 60 E. of Cactus Spring may be the 
gossan of a pyrite vein. Malachite stains occur on joint surfaces in 
the biotite andesite one-half mile southeast of Cactus Spring. 
HILLS BETWEEN THE CACTUS AND KAWK'II RANGES. 
TOPOGRAPHY AND GEOGRAPHY. 
Lying between the Cactus and Kawich ranges is a rather broad 
ridge of north-south trend, from which low domes arise. The south- 
ern pari of the ridge is a mesa sloping gently southward, evidently 
once a portion of Pahute mesa, but now separated from it as a result 
of erosion. The hills are bare of timber. A small seep, dry in sum- 
mer, is Located in the northern part of the ridge. 
GENERAL GEOLOGY, 
The formation- of these hills, from the oldest to the youngest, are 
the following: Eureka quartzite, rhyolite. biotite andesite. and 
basalt. 
SEDIMENTARY ROCKS. 
Eureka (?) quartzite. — Mr. T. C. Spaulding states that a small hill 
on the north of the range is composed of lilac-gray quartzite. The 
quartzite is rather coarse grained and contains some tiny pebbles of 
kaolinized feldspar and red jasperoid. The similarity of this rock 
to that of Quartzite Mountain in the Kawich Range indicates that it 
i- probably the Eureka quartzite. 
IGNEOUS ROCKS. 
Rhyolite. — The rhyolites are similar to those of the Cactus Range 
and are presumably contemporaneous. Slightly vesicular facies are, 
however, present. 
Biotite andesite. — Masses of dark-gray biotite andesite identical 
with that of the Cactus Range intrude the rhyolite in the north- 
western portion of the hills. 
Basalt. — The greater portion of these hills is composed of black 
basalt with dense groundmass. The phenocrysts are striated feld- 
spar, black pyroxene, and pellucid olivine, the feldspar and pyroxene 
showing a rude flow alignment. Vertical columnar jointing is well 
