D defs.my
Entry 1 sense Webster, 1913

Iceland spar

/īs'-lənd spär/ · Ice·land spar · IPA
01 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 st…
  1. 1.
    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.(Min.) See: Calcite