CHARACTER AND EXTENT OF SECONDARY DEPOSITS. 233 



by wavy dark lines which lie close together, giving an appearance some- 

 what like granite or gneiss, so that the plaster made from it is called by 

 the company " granite cement plaster." The lower part of the stratum 

 is compact, and contains rounded crystals of selenite with dark mottled 

 surfaces. It thus bears a close resemblance to the Solomon gypsum 

 already described, although the crystals are usually large, averaging 

 about two inches by one. These are the only two localities in this cen- 

 tral area where the gypsum rock is used for plaster. 



Secondary Gypsum Deposits. 



general character of the material. 



At a number of places in the central area occur interesting secondary 

 deposits of gypsum which form the basis of the greater portion of the 

 plaster manufacture. This material is locally called " stucco," " gypsum 

 dirt," and the like. It is a granular dirt found in low swampy ground, 

 and is dark colored in place, but on drying assumes a light ash gray 

 color. It is soft and incoherent, so that it is readily shoveled into cars, and 

 it is ready for calcining with less labor and. expense than is required in 

 working the solid rock. 



At the present time four of these deposits are opened in the central 

 area, plaster being now made at three of them, and a fifth is worked to 

 the north in Clay county. 



DISCOVERY AND EXTENT OF THE AREAS. 



The first deposit was discovered by Mr John Tinkler in the spring of 

 1873, near Gypsum City, when running a fire guard around a field. In 

 1889 he with others formed the Saline County Plaster Company, which 

 built a mill at the edge of town. This was afterward sold to the Acme 

 Cement Plaster Company, but they no longer use either the mill or the 

 deposit. In 1892, 7,000 tons of plaster were sent from this mill to Chicago 

 for the World's Fair buildings. This deposit covers an area of 12 acres 

 and lies close to the surface with little or no cover. The maximum depth 

 is 17 feet, while the average is 8. It resembles very much a fine sand 

 bed or loess formation, and there is a tendency to break in smooth planes 

 or joints. Organic matter occurs through it, and underneath is a layer 

 of clay, and below this a deposit known as " black gypsum," which is con- 

 sidered worthless. On the east side occur strong springs. The top of 

 the deposit is 20 feet above the water in Gypsum creek, a quarter mile 

 to the west, and it lies in the valley of a small tributary creek. In a 

 well dug on the hill above the deposit rock gypsum of good quality was 



