394 F. A. WILDER THE ORIGIN OF GYPSUM 



A Classification suggested 



The following classification of extensive gypsum deposits according to 

 origin is suggested : 



A. Deposits formed by concentration of material disseminated through sedi- 



ments : 



1. In inland basins. 



2. On the surface : 



o, by springs; 



I), as efflorescence. 



a', further concentrated by wind. 



&', further concentrated in slight depressions by sur- 

 face waters. 



3. In fissures, cavities, and as replacements. 



B. By alteration : 



1, of carbonates ; 



2, of anhydrite. 



C. Deposits formed directly by evaporation of sea-water. 



