Iceland spar

American  

noun

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

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Iceland spar British  

noun

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

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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.

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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

I now remove the analyzer, and put in its place the piece of Iceland spar with which we have already illustrated double refraction.

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

An able optician, named Nicol, cut a crystal of Iceland spar in two halves in a certain direction.

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

The paper also contains an account, although not an exhaustive one, of the various polarizing prisms which have from time to time been constructed by means of different combinations of Iceland spar.

From Scientific American Supplement, No. 441, June 14, 1884. by Various

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 Tyndall, John