Search Result for "iceland spar":
Wordnet 3.0

NOUN (1)

1. a transparent calcite found in Iceland and used in polarizing microscopes; 



The Collaborative International Dictionary of English v.0.48:

Iceland spar \Ice"land spar`\ (Min.)
   A transparent variety of calcite, the best of which is
   obtained in Iceland. It is used for the prisms of the
   polariscope, because of its strong double refraction. Cf.
   Calcite.
   [1913 Webster]


WordNet (r) 3.0 (2006):

Iceland spar
    n 1: a transparent calcite found in Iceland and used in
         polarizing microscopes