CHAPTER X. 



SILVER AND GOLD, CONTINUED. ROCKY MOUNTAIN REGION, 

 WYOMING, THE BLACK HILLS, MONTANA, AND IDAHO. 



WYOMING. 



2.10.01. Geology. The southeastern part of Wyoming is 

 in the Prairie region, the southwestern in the Plateau. The 

 Rocky Mountains shade out more or less on leaving Colorado, 

 but are again strongly developed in northern Wyoming. The 

 northwestern portion contains the great volcanic district of the 

 National Park, and the northeastern, a part of the Black Hills. 

 The Cretaceous and Tertiary strata chiefly form the plains and 

 plateaus. Granite and gneiss constitute the central portion of 

 some of the greater ranges. Paleozoic rocks are very subordinate. 

 The resources in precious metals are small, consisting chiefly of 

 gold in quartz veins in the gneisses, schists, and granites of Still- 

 water County. The great mineral wealth of the State is in coal. 

 The iron mines have already been mentioned (2.03.09), and the 

 copper (2.04.27). 1 



THE BLACK HILLS. 



2.10.02. Geology. The Black Hills lie mostly in South Da- 

 kota. They consist of a somewhat elliptical core of granite 

 and metamorphic rocks, with a north and south axis, and on 

 these are laid down successive strata of Cambrian, Carbonifer- 



1 H. M. Chance, "Resources of the Black Hills and Big Horn Coun- 

 try, Wyoming," M. E., XIX., p. 49. T. B. Comstock, "On the Geology 

 of Western Wyoming," Amer. Jour. Sci., iii., VI. 426. S. F. Emmons, 

 Tenth Census, Vol. XIII. , p. 86. F. M. Endlich, "The Sweetwater Dis- 

 trict," Hayderfs Survey, 1877, p. 5 ; " Wind River Range Gold Washings," 

 p. 64. A. Hague, " Geological History of the Yellowstone National Park," 

 M. E., XVI. 783. See also F. V. Hayden, Amer. Jour. Sci., iii., III. 105, 

 161. F. V. Hayden, Rep. for 1870-72, p. 13; also Amer. Jour. Sci.,i\., 

 XXXI. 229. A. C. Peale, " Report on the Geology of the Green River Dis- 

 trict," Hayden's Survey, 1877, p. 511. Raymond's Statistics West of the 

 Rocky Mountains. 



