Iceland spar

American  

noun

1. a transparent variety of calcite that is double-refracting and is used as a polarizer.

---

Iceland spar British  

noun

1. a pure transparent variety of calcite with double-refracting crystals used in making polarizing microscopes

---

Iceland spar Scientific  

/ īs′lənd /

1. A form of calcite that is transparent and causes light passing through it to refract in two directions (forming a double image of an object seen through it). Iceland spar occurs in perfect rhombohedrons and is used in optical instruments.

---

Etymology

Origin of Iceland spar

First recorded in 1820–30

Example Sentences

See Examples For:

Iceland spar

Discovered in the 17th Century, polarization has become an elaborate science using small, costly, natural crystals like Iceland spar.

From Time Magazine Archive

Now the refractive index of Iceland spar is, for the extraordinary ray less, and for the ordinary greater, than for Canada balsam.

From Six Lectures on Light Delivered In The United States In 1872-1873 by John Tyndall

Here is a mass of Iceland spar, which also cleaves in three directions, not at right angles, but obliquely to each other, the resulting solid being a rhomboid.

From The Glaciers of the Alps Being a narrative of excursions and ascents, etc. by John Tyndall

A, simple lens; B, piece of Iceland spar with glass prisms on ends to square them up; C, square hole.

From A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public by Frank Bertram Wade

Here we are helped by the property of Iceland spar, which is able to split up a ray into two divergent rays.

From Colour Measurement and Mixture by W. de W. Abney