Iceland spar
/ˈʌɪslənd
/noun [mass noun]
A transparent variety of calcite, showing strong double refraction.Nodules filled with clear double-refractive Iceland spar with celadonite inclusions have also been found here....
- The large, transparent crystals known as Iceland spar, however, are pure calcite.
- Certain crystals will split incoming light into two separate rays; Iceland spar is one such crystal, as are calcite and quartz.