MINERAL DEPOSITS OF THE BITTERROOT RANGE AND CLEAR- 
WATER MOUNTAINS, MONTANA. 
By Waldemar Lindgren. 
INTRODUCTION. 
In L899 a geological reconnaissance was undertaken of the country 
between the Bitterroot Valley in Montana on the east and the Lewis- 
ton Plateau on the west. During the reconnaissance I was assisted 
by Mr. G. W. Stose, of the United States Geological Survey, and Mr. 
H. R. Johnson. 
The region visited is bordered on the south by the Salmon River 
and on the north by the North Fork of the Clearwater. The fertile 
Bitterroot Valley lies at the eastern foot of the imposing range of the 
Bitterroot. This range, which attains an elevation of 11,000 feet, 
westward merges into the great dissected plateau of the Clearwater! 
Mountains, which in turn at their western edge descend rather 
abruptl} 7 to the plateaus of Camas Prairie and Cold Spring Prairie, 
forming part of the great Columbia River lava plateau. This latter 
plateau has a general elevation of 2,500 to 3,000 feet, and is built up 
of horizontal lava flows. 
From great glacial cirques in the western slopes of the Bitterroot 
Range the Salmon River and the several forks of the Clearwater 
River find their way westward in canyons from 3,000 to 5,000 feet deep. 
The canyon of the Salmon especially is remarkable for its great length 
and depth. In the lower plateau country these rivers flow in more 
sharply incised but less deep canyons, which continue to their junc- 
tion with the master stream, the Snake River. 
The area indicated forms a wild and very sparsely populated moun- 
tain region, heavity timbered except on the highest ridges, which 
usually show clear evidence of glacial action. The geology is com- 
paratively simple. The main Bitterroot Range and the larger part of 
the Clearwater Mountains consist of a massive biotite-granite, or, 
defining it more correctly, a quartz-monzonite, which is the northward 
continuation of the great batholith of the same rock which occupies 
so large an area in south-central Idaho. In the latter region this 
intrusive mass is of post-Carboniferous and probably late Mesozoic 
age, and there is no reason to believe that the granite of the Clear- 
water and the Bitterroots is of different age. 
66 
