DETAILS OF HIGHLANDS. 23 
prospects have not been extensively developed owing to the inaccessi- 
bility of the region. 
Overlying the granite south of Artillery Peak occur thick masses 
of effusive rock similar in appearance to the older effusives of the 
Aquarius Mountains to the east, but separated from them by erosion. 
Quaternary lavas also occur in small quantities included in and over- 
lying the gravels in Signal and Williams canyons. 
WHITE HILLS. 
Location, — The White Hills, located in the north-central part of the 
region described, are the southward continuation of the Virgin Moun- 
tains of southeastern Nevada, and are separated from them by Virgin 
Canyon. 
Topographic features. — The White Hills consist of many more or 
less isolated peaks and groups of hills rising a few hundred feet above 
the plains on either side of them, and are inconspicuous as compared 
with neighboring highlands. 
Rock masses. — Granite similar in general appearance to that 
beneath the Cambrian formation of the Grand Wash Cliffs occurs in 
these hills, and is more or less mineralized, several gold prospects hav- 
ing been developed in it. Quartzites and argillites, apparently of 
pre-Cambrian age, occur in the hills south of Virgin Canyon. The 
Tertiary rhyolites and andesites are found from Squaw Peak to the 
southern end of the White Hills, and occur as light-colored beds of 
tuff and ash and as flow sheets. 
CERBAT MOUNTAINS. 
Location. — The Cerbat Mountain range, about 30 miles long, lies 
south of the White Hills, between the Hualpai and the Detrital- 
Sacramento valleys. 
Topographic features. — The mountains are high, attaining a maxi- 
mum altitude of about 7,000 feet in Cherums Peak, and have been 
deeply eroded. At the southern end of the range they break down 
and merge into a dissected plateau. 
Rock masses. — The Cerbat Mountains are composed mainly of 
granitic rock similar in general appearance to the pre-Cambrian gran- 
ites of the cliffs region to the east. These are intersected and more 
or less completely surrounded by effusive rocks. 
Along the western base of the range rhyolite and andesite occur at 
intervals, but are frequently eroded away or covered with wash. 
Near the southern end of the mountains they overlie the granite in 
extensive beds of ash, tuff, and flow, originally 1,000 feet or more in 
thickness. The igneous rocks are evidently due to a long series of 
eruptions, Hows, and beds of tuff alternating (see PI. IV, A), and both 
being cut by dikes and covered by younger effusives. 
