Source : Webster's Revised Unabridged Dictionary (1913)

Heulandite \Heu"land*ite\, n. [After Heuland, an English
   mineralogist.] (Min.)
   A mineral of the Zeolite family, often occurring in
   amygdaloid, in foliated masses, and also in monoclinic
   crystals with pearly luster on the cleavage face. It is a
   hydrous silicate of alumina and lime.

Source : WordNet®

heulandite
     n : a group of minerals of the zeolite family consisting of a
         hydrous aluminum silicate of sodium and calcium