94 NEW YORK STATE MUSEUM 



Portland cement mills; the product of calcined plasters and of land 

 plaster each showed a slight decrease as compared with the returns 

 for 1916. The 1918 output at the mines of 531,038 short tons is 

 a decrease of 75,230 tons from the 19 17 production, but with the 

 higher prices obtained shows an increase in value of the products 

 sold of $633,279. 



Uses. Recent experimental tests with gypsum in agriculttire 

 have revived interest in the use of land plaster, indicating that 

 it has a positive fertilizing value for some crops, notably grains, 

 grasses and legumes. Its principal function is as carrier of sulphur, 

 which enters into the structure of many plants in proportions com- 

 parable to those of phosphorus, the basis of most prepared fertilizers- 

 Gypsum also improves the mechanical condition of soils and effects 

 certain beneficial chemical reactions. 



Portland cement manufacttire calls for about one-third of the mine 

 product of the State. For this purpose the rock is crushed to smal^ 

 size, usually through one-half inch mesh. About two per cent is 

 added to the clinker as it comes from the rotary kilns and is ground 

 with it. Its function is to delay the set of the cement. The demand i 

 is for a high-grade gypsimi, and sales are made on the basis of the j 

 sulphuric acid content. ] 



The major portion of the mine product is calcined into stucco> | 

 usually in plants operated by the mining companies. The stucco \ 

 is admixed with a small amount of retarder and some fiber like hair j 

 or shredded wood and becomes hard wall plaster. Such plasters i 

 are harder and attain their final set much quicker than lime plasters. 

 A constantly increasing proportion of stucco is being converted ^ 

 Into such materials as plaster board, wall board, blocks and tiles, , 

 the manufacture of which is one of the recent developments that j 

 seems to promise most for the future of the industry. Plaster ] 

 board and wall board are sheets of stucco lined on either side with ' 

 paper and designed to be applied directly to the studding, without 

 the use of lath. Wall board requires no coat of plaster to give a 

 finished appearance. Plaster board if applied to inside walls is i 

 given a single coat, but it is also used on the outside for sheathing i 

 and as lining in the place of lumber. Gypsum block and tile are j 

 made in a variety of sizes and shapes, taking the place of clay articles i 

 in fire-proof construction for floors, partitions and roofs. 



Occurrence. The supply of gypsum is obtained from a single \ 

 series of deposits which is confined to the Salina stage of the ! 

 Silurian system. The main occurrence of the Salina strata is repre_ ' 



