DuckCorp Dico

Found one definition

1.                 From The Collaborative International Dictionary of English v.0.48:
                   
   
   
                   
                     
   Cawk \Cawk\ (k[add]k), n. [Prov. E. cauk limestone. A doublet of
      chalk.] (Min.)
      An opaque, compact variety of barite, or heavy spar. [Also
      written cauk.]
      [1913 Webster]