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

Crystals like calcite, also called Iceland spar, can reveal the direction of polarization, a bit like a prism that reveals the rainbow within white light.

From Washington Post

Light from the sky is polarised and, as he discovered in 2011, looking through a piece of Iceland spar reveals the direction of polarisation, and thus the direction of the sun, to within 5°.

From Economist

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

From Project Gutenberg

Spar, sp�r, n. a term applied by miners to any bright crystalline mineral, and adopted by mineralogists in the names of a number of minerals—calcareous spar, fluor spar, Iceland spar, &c.—adj.

From Project Gutenberg

He and his colleagues have been experimenting with a mineral called Iceland spar.

From Economist