MICROSCOPICAL CHARACTER OF SECONDARY DEPOSITS. 



235 



ness, not consolidated and still containing water. Its main use in those 

 regions has been as fertilizer and for whitewash. 



MICROSCOPICAL CHARACTER. 



A microscopical examination of the material of the central Kansas 

 deposits shows a considerable uniformity in character, as represented in 

 figure 3. The dirt is seen to consist of a mass of small angular gypsum 

 crystals of varying size. Perfect crystals are found, but most of them 

 have their terminations somewhat rounded by solution. They are not 

 transported crystals, but have clearly crystallized in place. Mingled 

 with the gypsum crystals are small quartz crystals, seen especially in 

 the Longford deposit. There is 

 also a considerable amount of 

 lime carbonate poorly crystal- 

 lized and traces of organic 

 matter. 



Medicine Lodge Deposits. 



character of the gypsum. 



The Medicine Lodge gypsum is 

 white, and in the lower .portion 

 of the stratum it is very compact. 

 This portion is used at the Medi- 

 cine Lodge mill for manufacture 

 of terra alba. The upper portion 

 has more of the sugary texture 

 and is used in the manufacture 

 of wall plaster. The satinspar which is found through the red beds be- 

 low the gypsum is in the form of wavy plates, with perpendicular needles 

 and variable in character. Some is soft and readily crumbles, while 

 other portions are compact and glassy in appearance. 



EXTENT OF THE AREA. 



This southern gypsum area is the largest in Kansas, and, with its con- 

 tinuation in Oklahoma and Texas, forms the largest gypsum area in the 

 United States. The rock extends from near the town of Medicine Lodge 

 westward through Barber and Comanche counties, southward into Okla- 

 homa and Texas, and passes under the Tertiary gravels to the north. 

 The trend of the deposit is the characteristic one of the state — northeast 

 to southwest. 



Figure 3. — Gypsum Dirt from central Kansas 

 (magnified 60 times). 



XXXIV— Bull. Geol. Soc. Am.. Vol. 



