222 KEMPS ORE DEPOSITS. 



miles north of Helena, in the town of Marysville, is the Drum- 

 lummon group of veins, which carry refractory silver and gold 

 ores, in a quartz gangue, on the contact between a granite knob 

 and the surrounding metamorphic schists. There are also other 

 veins in the granite. Dikes of intrusive rocks occur associated 

 with the ore bodies. 1 



2.10.12. Missoula County. In the northwestern corner of the 

 State is a region of very recent development, and more especially 

 since the Northern Pacific Railroad has been built through it. At 

 Iron Mountain and elsewhere mining districts are growing up, but 

 available descriptions have not yet been received. (See paper by 

 G. E. Culver, cited under 2.10.04.) In Meagher County, in the 

 central part of the State, there are a number of mining districts 

 in the Little Belt Mountains. Neihart is the location of some 

 rich silver mines, and is now connected with Great Falls by rail. 

 Other camps are as yet too remote for profitable working. 



IDAHO. 



2.10.13. Geology. The southern part of the State extends 

 into the alkaline deserts of the Great Basin and is dry and barren. 

 North of this is the Snake River Valley, which is filled by a great 

 flood of recent basalt which stretches from the Wyoming line 

 nearly across the State. North of the Snake River a large area 

 of granite appears in the western portion and contains many 

 mines. Extensive deposits of gravel also occur. Metamorphic 

 rocks and Paleozoic strata largely constitute the northern portion 

 of the State, and are penetrated by many igneous intrusions. The 

 eastern part lies on the western slopes of the Bitter Root Moun- 

 tains, whose general geology was outlined under Montana. The 

 geology of Idaho has been but slightly studied, and the few re- 

 liable records have resulted from the scattered itineraries of Hay- 

 den's survey, isolated mining reports, and the collections of the 

 Tenth Census. 2 



1 J. E. Clayton, " The Drumlummon Group of Veins," etc., Engineer- 

 ing and Mining Journal, Aug. 4 and 11, 1888, pp. 85, 106. S. F. Emmons, 

 Tenth Census, Vol. XIII., p. 97. 



3 G. F. Becker, Tenth Census, Vol. XIII., 52. F. H. Bradley, Hay den's 

 Survey, 1872, p. 208. F. V. Hayden, Ann. Rep., 1871, pp. 1, 147 ; 1872, p. 

 20. J. S. Newberry, "Notes on the Geology and Botany along the North- 

 ern Pacific Railroad," Annals N. Y. Acad. Sci., III. 252. Raymond's Re- 

 ports on Mineral Resoures West of the Rocky Mountains. O. St. John, 

 Hay den's Survey, 1877, p. 333 ; 1878, p. 175. 



