Calcareous spar

Calcite \Cal"cite\ (k[a^]l"s[imac]t), n. [L. calx, calcis,
   lime.] (Min.)
   Calcium carbonate, or carbonate of lime. It is rhombohedral
   in its crystallization, and thus distinguished from
   aragonite. It includes common limestone, chalk, and marble.
   Called also {calc-spar} and {calcareous spar}.
   [1913 Webster]

   Note: Argentine is a pearly lamellar variety; aphrite is
         foliated or chalklike; dogtooth spar, a form in acute
         rhombohedral or scalenohedral crystals; calc-sinter and
         calc-tufa are lose or porous varieties formed in
         caverns or wet grounds from calcareous deposits; agaric
         mineral is a soft, white friable variety of similar
         origin; stalaclite and stalagmite are varieties formed
         from the drillings in caverns. Iceland spar is a
         transparent variety, exhibiting the strong double
         refraction of the species, and hence is called doubly
         refracting spar.
         [1913 Webster]
    

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]