30 NEW YORK STATE MUSEUM 



GYPSUM 



Gypsum, the hydrous sulphate of calcium (CaS0 4 , 2H 2 0) occurs 

 in large quantities on the area of the Syracuse quadrangle and the 

 adjoining areas to the east and west. As its locus is in the Camillus 

 shales, its distribution in the area is indicated on the map by the 

 outcrop of the Camillus group. While it occurs at several different 

 horizons in the shales, the largest and most continuous bed is at 

 the top of the series immediately underlying the Bertie dolomite. 

 Nearly all the gypsum quarries will be found along the line of con- 

 tact of these two groups, the Bertie and the Camillus. 



The maximum thickness of the gypsum in the area is reached in 

 the quarries a mile south of Lyndon near the southeast corner of 

 the quadrangle, where it has a thickness of 60 feet from which it 

 varies to about 20 feet near the southwest corner of the map. The 

 deposit is not all pure gypsum but contains carbonates and argillace- 

 ous material ranging from 1 or 2 up to as high as 20 per cent of 

 the mass. The impurities are rather intimately mixed through 

 the deposit, and the clayey matter appears to make up a larger per- 

 centage of the mass than it really does. 



There is sufficient quantity of impurities in the gypsum to dis- 

 color it and make it unfit for finishing plasters, but the impuri- 

 ties do not seriously injure it for use in portland cement and land 

 plaster. In the early days of the industry in this region nearly all the 

 product was used for land plaster, for which purpose it was ground 

 into a fine flour before being applied to the soil. Mills for this 

 purpose are located at Jamesville and Fayetteville, but they are 

 falling into disuse as less and less of the gypsum is being used for 

 this purpose and more of it is being used in the cement industry. 



The gypsum is added to portland cement as a retarder to prevent 

 the cement from setting or hardening too quickly. While only a 

 small percentage (2^ per cent or less) of gypsum is used in the 

 cement, the aggregate amount so used is large owing to the enor- 

 mous consumption of cement which has increased tremendously in 

 the last one or two decades. It is for this purpose that much of 

 the gypsum now quarried in this county is sold. 



The most important application of gypsum of course is in the 

 manufacture of wall plasters, in which it is replacing the lime 

 mortar formerly used almost exclusively for this purpose. It is 

 not only used as a mortar to apply directly to the wall, but some 

 of it is made up into thin sheets with layers of paper, known as 

 plaster board, which is nailed to walls and ceilings and does away 

 with lath. A thin coat of plaster is put on top of the plaster board 



