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Iceland spar, formerly known as Iceland crystal, is a transparent variety of calcite, or crystallized calcium carbonate, originally brought from Iceland, and used in demonstrating the polarization of light (see polarimetry). It occurs in large readily cleavable crystals, easily divisible into rhombs, and is remarkable for its double refraction. Historically, the phenomena of this crystal have been studied at length by Huygens and Newton.
It has been speculated that the Vikings used the light-polarizing property of Iceland spar, which they called sunstone (a different mineral than the gem-quality sunstone), to tell the direction of the sun on cloudy days, for navigational purposes.
In 2007, Gabor Horvath from Eotvos Lorand University in Budapest, Hungary confirmed that the polarization of sunlight in the Arctic can be detected using a sunstone.
Thomas Pynchon references the doubling property of Iceland spar in his 2006 novel Against the Day. A section of the novel is entitled "Iceland Spar".
Phillip Pullman references the doubling property of Iceland spar in his 2000 novel The Amber Spyglass, the third volume in the His Dark Materials trilogy.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Iceland_spar". A list of authors is available in Wikipedia.|