COMPOSITION, DISTRIBUTION, AND EXCAVATION OF GYPSUM. 23 



rate of production the known deposits will last about twenty-five 

 years." 



Oklahoma. Oklahoma occupies a central position in the belt of 

 country which carries extensive gypsum deposits all the way from the 

 northern part of Kansas into central Texas (see Fig. I). Within its 

 borders the number and thickness of the beds appear to be greater than 

 to the north and south. " The amount of gypsum appears to be inex- 

 haustible. With perhaps two exceptions, each of the western counties 

 contains enough material to supply the United States for an indefinite 

 length of time, and there are in addition considerable deposits in the 

 eastern part of the Territory." The gypsum in Oklahoma may be con- 

 sidered as occurring in four regions: (1) the Kay County region; (2) the 

 main line of gypsum hills, extending from Canadian County northwest 

 through Kingfisher, Elaine, Woods, and Woodward counties to the 

 Kansas line; (3) the second gypsum hills, parallel with the main gypsum 

 hills, and from 50 to 70 miles farther southwest, which extend from the 

 Keechi Hills, in southeastern Caddo County, northwestward through 

 Washita, Custer, Dewey, and Day counties; and (4) the Greer County 

 region, occupying the greater part of western Greer County and the 

 extreme southeastern corner of Roger Mills County. 



The deposits in Kay County consist of earthy gypsum, or gypsite. 

 In the other three regions rock gypsum predominates, although there 

 are numerous localities where earthy gypsum occurs in workable bodies. 



Oregon. Gypsum occurs in Oregon in only one known and exploited 

 locality. This is on the eastern border of the State, near the middle 

 point of the boundary-line, on a ridge dividing Burnt River and Snake 

 River. A plaster-plant located at Lime uses material from this locality. 



South Dakota. "In the Black Hills uplift there is brought to the 

 surface an elliptical outcrop of the Red Beds surrounding the high ridges 

 and plateaus of the central portion of the Black Hills. The area is 

 about 100 miles long by 50 miles wide, and the outcrop zone has an 

 average width of 3 miles, except in a few districts where the rocks dip 

 steeply, where it is much narrower. The formation consists mainly 

 of red sandy shales, with included beds of gypsum at various horizons, 

 some of which are continuous for long distances, while others are of 

 local occurrence. The thickness of the deposits varies greatly, but in 

 some districts over 30 feet of pure white gypsum occur, and nearly 

 throughout the outcrop of the formation it contains deposits of suffi- 

 cient thickness and extent as to have commercial value. 



"The gypsum is a prominent feature about Hot Springs. Here the 

 principal beds occur about 60 feet above the base of the formation and 



