THE GYPSUM INDUSTRY OF NEW YORK STATE 



By William C. Clarke, E. M. 



Gypsum is the sulphate of lime and contains lime 32.6%, 

 sulphuric acid 46.5^, water 20.9%. Its specific gravity when 

 pure varies between 2.314 and 2.328. 



The crystallized variety is known as selenite. The pure 

 mineral is CaS0 4 + 2 2 H z O. Oxides of iron and silica are 

 also present. The crystalline variety occurs in the quarries 

 in but small quantities. It has a pearly lustre and a cleav- 

 age similar to that of mica and splits into very thin plates. 

 The pure massive mineral resembles marble in texture and 

 color and is quarried under the name of alabaster. 



When exposed to a heat of not over 260 F. gypsum loses 

 its water of crystallization and if reduced to powder it has 

 the property of recombining with water when mixed with it 

 and forming a solid mass. This recombination does not 

 take place if the material is overheated. 



The geological occurrence of gypsum has already been 

 described and its geographical distribution is shown on the 

 accompanying map. 



Selenite and anhydrite have been found in Niagara Co. 

 near Lockport. 



The gypsum occurs in beds of considerable regularity, 

 plainly showing in places its original deposition from water. 

 No evidence of gypsum can be found east of Hobokenville, 

 Madison Co. Toward its eastern limit the gypsum is of 

 a much darker and earthy type. The dark color of the 

 gypsum is said to be due to the presence of carbonaceous 

 matter and not to metallic oxides, but it is probable that 



