REVIEWS 
Geology.—Reconnaissance of the Jarbidge, Contact and Elk Moun- 
tain Mining Districts, Nevada. By F. C. SCHRADER. Bull. 
U.S. Geological Survey No. 497, pp. 162, with maps, sections, 
and illustrations. 1912. 
Geography.—The districts are in Elko County in northeastern 
Nevada near the Idaho state line. They are contained in an east- 
west rectangular area about 35 miles long by 26 miles wide, the Jarbidge 
district being in the western part, the Contact district in the eastern 
part, and the Elk Mountain district in the northern part. Geologically 
and mineralogically the Elk Mountain district is a small-scale replica 
of the Contact district. 
The area is about 50 miles distant from the Twin Falls Branch of 
the Oregon Short Line Railroad on the north and from the Southern 
Pacific Railroad on the south. It lies in the northeastern part of the 
upland region known as the Nevada Plateau. It is mainly on the 
southern rim of the Snake River drainage basin, whence it extends 
across the divide and includes a small part of the adjacent Great Basin 
on the south. It lies at the general elevation of about 6,000 feet, but 
it is mostly mountainous and has a vertical range of nearly 6,000 feet 
and culminates at about 11,000 feet in the Jarbidge Mountains on the 
west. In the western part the drainage issues northward through 
the Bruneau River, and in the eastern part easterly, thence northward 
through the Salmon River, both rivers being main south-side tributaries 
of the Snake. 
Geology.—The area is in a region of fundamentally Paleozoic sedi- 
mentary rocks seemingly Carboniferous. They consist principally of 
quartzite, limestone, shale, and slate, folded, faulted, intruded by Cre- 
taceous (?) granodiorite, flooded and capped by Tertiary eruptives, 
principally rhyolite, and overlain by Tertiary lake beds and Quaternary 
gravel and alluvium. 
In the Jarbidge district the rocks are principally rhyolites. Here 
the Paleozoic sediments are exposed only on the west. They consist, in 
ascending order, of quartzite, limestone, and shale aggregating about 3,000 
feet (?) in thickness and they dip steeply to the north. The rhyolites 
are separable into two distinct groups, old rhyolite of Miocene (?) age 
37° 
