52 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
The shale is fine grained and thin bedded. It is in most places 
olive green, although locally brilliant rose or purplish pink, while red 
is imparted to weathered exposures by iron stains. Arenaceous fanes 
are rare. Rather commonly the shale breaks down into pencils which 
are produced by the intersection of two closely spaced joint systems 
ami bedding planes. Veins in the shale are usually quartz. 
No fossils were found in these beds, but on lithologic grounds they 
are probably Lower Cambrian. Turner" so considers the extension 
of these rocks in the adjoining Silver Teak quadrangle. 
Older alluvium. — The road from Alkali Spring to Lone Mountain 
passes through a gap in the ridge south of the General Thomas mine. 
The -addle and the low hill- on either side are composed of fragniental 
material lithologically like the Recent alluvium deposits, except that 
it i- somewhat weathered. Erosion has cut it into a number of low 
hills. This deposit is the remnant of an old alluvial slope, and is 
tentatively correlated with the older alluvium of Pliocene-Pleistocene 
age in Death Valley. 
[GNEOl S ROCKS. 
Granite. — Lone Mountain is a batholith of granite which has 
pushed up tin 4 Cambrian rocks on it- border, and into these apophy- 
ses extend. The batholith covers about 1 1 square miles at the north] 
wesl corner of the area mapped. 
The granite is light gray in color and of either medium or coarse 
grain. The constituents, which in coarse-grained types reach a 
maximum diameter of one-half inch, are white feldspar, smok$ 
quartz, and biotite. Phenocrystic feldspars 'J inches long and one- 
half inch wide are locally present. In some exposures the con- 
stituents possess a parallel arrangement, probably original. Epidotd 
films are developed along some joint surfaces, while on others 
flattened, distorted cubes of limonite after pyrite occur. Muscovite 
films cover plane- of movement. 
An excellent sheeting, the joints being from 1 to 3 feet apart, 
cuts the granite and impart- to many portions of Lone Mountain a 
sedimentary aspect. The granite weathers into rounded slablike 
joint blocks stained by limonite. and in consequence the mountain 
mass is yellowish white in color. The mountain itself has a very 
rugged topography characterized by knife-edge divides and deep- 
cut, steep valleys. The foothills and inliers in the wash have strong 
tendencies to dome form. 
Under the microscope the granite is seen to be uneven grained 
and rather poor in both biotite and quartz. With orthoclase and 
microcline is a little oligoclase. Titanite rhomboids are very abun- 
dant, and the other accessory minerals are magnetite, apatite, and 
a Op. cit. 
