The Collaborative International Dictionary of English v.0.48:

Calcareous \Cal*ca"re*ous\, a. [L. calcarius pertaining to lime.
   See Calx.]
   Partaking of the nature of calcite or calcium carbonate;
   consisting of, or containing, calcium carbonate or carbonate
   of lime.
   [1913 Webster]

   Calcareous spar. See as Calcite.
      [1913 Webster]

WordNet (r) 3.0 (2006):

calcareous
    adj 1: composed of or containing or resembling calcium carbonate
           or calcite or chalk [syn: calcareous, chalky]