The Collaborative International Dictionary of English v.0.48:

Mesolite \Mes"o*lite\ (?; 277), n. [Meso- + -lite.] (Min.)
   A zeolitic mineral, grayish white or yellowish, occuring in
   delicate groups of crystals, also fibrous massive. It is a
   hydrous silicate of alumina, lime, and soda.
   [1913 Webster]