gypseous

from The Collaborative International Dictionary of English v.0.48

Gypseous \Gyp"se*ous\ (j[i^]p"s[-e]*[u^]s), a. [L. gypseus. See
   {Gypsum}.]
   Resembling or containing gypsum; partaking of the qualities
   of gypsum.
   [1913 Webster]