GYPSU:\[ DEPOSITS OF NEW YORK 6j 



the shores of the Caspian sea are now depositing salts, while the 

 waters of K-liaraboghaz, wliich are almost shut off from the sea by 

 long spits that leave only a shallow cliann el between them, are in 

 process of concentration and are fed by a surface current that is 

 estimated to bring 350,000 tons of salt a day into the gulf. 



According to tliis theor}' the evaporating basin is in effect a con- 

 tinuous salt pan and the thickness of the deposits that might be 

 formed is limited only by its depth. 



Formation by conversion of limestone in place. Where ground 

 waters are supplied more or less constantly with available sulfuric 

 acid, from pyritic shales for example, it is not improbable that they 

 may convert large masses of limestone into gypsum during the 

 course of time. The gypsum would retain perhaps the bedded 

 structures of the limestone and would thus closely resemble tlie 

 deposits from sea water. Just what importance is to be placed upon 

 this method in relation to stratified deposits in general can not be 

 stated, though some geologists have advocated its application to 

 extensive occurrences, including those of New York State. 



There is no doubt that this process operates in 'a small way. 

 Scattered masses and crystals of gyps'im formed by the reaction of 

 acid sC'lutions upon lime are found in the clay beds along the Hud-. 



n river. The indurated shales upon which the clays rest are 

 unpregnated with pyrite, which affords a source of sulfuric acid, 



hile the claA's themselves contain lime carbonate to the amount of 

 cveral-per cent. The gypsum is- often well crystallized in detached 

 individuals but has no economic value. 



Gypsum deposited by ground waters. Ground waters holding 



calcium sulfate in solution may come to rest in joints, fissures or 



ther openings in rocks, where evaporation may bring them to the 



)int of saturation. The gypsum usually separates in the form of 



lenite or in the fibrous aggregate known as satin spar. The gyp- 

 .um strata with their inclosing rocks are frequently veined and 

 seamed by such secondary deposits. The cavities thus filled may 

 have been very narrow at first, but were widened gradually by solu- 

 tion and possibly as well by the expansive force of the growing 

 crystals. The force of crystallization is regarded by some geologists 

 as an important factor in the formation of cavities occupied by 

 minerals deposited from solution. Though its magnitude is not 

 definitely establish.cd, it is considered in general to be measurable 

 by the crushing strength of the minerals themselves. If such be 

 the case, it is apparent that large masses of gypsum might bo Iniilt 



