The Collaborative International Dictionary of English v.0.48:

Decalcify \De*cal"ci*fy\, v. t. [imp. & p. p. Decalcified; p.
   pr. & vb. n. Decalcifying.]
   To deprive of calcareous matter; thus, to decalcify bones is
   to remove the stony part, and leave only the gelatin.
   Decalcomania

WordNet (r) 3.0 (2006):

decalcify
    v 1: lose calcium or calcium compounds
    2: remove calcium or lime from; "decalcify the rock" [ant:
       calcify]