Iceland spar
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).[1][2] It occurs in large readily cleavable crystals, easily divisible into rhombs, and is remarkable for its double refraction.[3][4] Historically, the phenomena of this crystal were studied at length by Christiaan Huygens and Isaac Newton.[5] Sir George Stokes also studied the phenomenon.[6]
Mines producing Iceland spar include many mines producing related calcite and aragonite as well as famously in Iceland,[7] productively in the greater Sonoran desert region as in Santa Eulalia, Chihuahua, Mexico[8] and New Mexico, United States,[9] as well as in the People's Republic of China.[10]
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[edit] Viking "sunstone"
It has been speculated that the sunstone (a different mineral than the gem-quality sunstone) mentioned in medieval Icelandic texts was Iceland spar and that Vikings used its light-polarizing property to tell the direction of the sun on cloudy days, for navigational purposes.[11][12]
In 2007, Ramón Hegedüs and his colleagues from Eötvös Loránd University in Budapest, Hungary, confirmed that the polarization of sunlight in the Arctic can be detected under cloudy conditions. Their research is reported in "The Proceedings of the Royal Society."[13] Further research in 2011 by Ropers et al. [14] , confirms that identifying the direction of the sun to within a few degrees in both cloudy and twilight conditions was possible using the sunstone and the naked eye. The process involves moving the stone across the visual field to reveal a yellow entoptic pattern on the fovea of the eye. The recovery of an Iceland spar sunstone from the Elizabethan ship Alderney that sank in 1592 suggests that the navigational technology may have persisted after the invention of the magnetic compass.
[edit] In literature
Thomas Pynchon refers to the doubling property of Iceland spar in his 2006 novel Against the Day.[15] A section of the novel is entitled "Iceland Spar".[16]
Phillip Pullman refers to the doubling property of Iceland spar[17] in his 2000 novel The Amber Spyglass, the third volume in the His Dark Materials trilogy.
[edit] References
- ^
This article incorporates text from the public domain 1913 Webster's Dictionary. - ^ "Iceland spar". Oxford English Dictionary. Oxford University Press. 3rd ed. 2001.
- ^ This article incorporates text from the public domain 1828 Webster's Dictionary.
- ^ Miers, Henry A., Mineralogy: an introduction to the scientific study of minerals. Nabu Press. ISBN 117785127X Chap. 6, p. 128.
- ^ This article incorporates content from the 1728 Cyclopaedia, a publication in the public domain.
- ^ Larmor, Joseph 2010. Retrieved January 2, 2011. Memoir and scientific correspondence of the late Sir George Gabriel Stokes, bart., selected and arranged by Joseph Larmor. Nabu Press. ISBN 1177142759 p. 269.
- ^ Russell, Daniel E . 17 February 2008. Retrieved December 31, 2010. "Helgustadir Iceland Spar Mine" mindat.org
- ^ Retrieved January 2, 2011. "Calcite"Granite Gap "Several variety names exist for calcite. Iceland Spar is an ice-clear variety that demonstrates the effect of double refraction or birefringence ... Young mountain ranges in Mexico and South America also host fine localities for calcite. They include Chihuahua, Chihuahua; the Santa Eulalia Dist., Chihuahua; Mapimí, Durango; Guanajuato, Guanajuato; and Charcas, San Luis Potosí; all Mexico"
- ^ Kelley, Vincent C. 1940. Retrieved December 31, 2010. "Iceland Spar in Mew Mexico". American Mineralogist, Volume 25, pp. 357-367
- ^ WANG Jing-teng, CHEN Hen-shui, YANG En-lin,WU Bo. 2009. Retrieved January 3, 2011. "Geological Characteristics of Iceland Spar Mineral Deposit of Mashan District in Guizhou". China National Knowledge Infrastructure, P619.2 doi:CNKI:SUN:KJQB.0.2009-33-061
- ^ The Viking Sunstone, from Polarization.net. Retrieved February 8, 2007.
- ^ Karlsen, Leif K. 2003. Secrets of the Viking Navigators. One Earth Press. ISBN 978-0972151504 220 pp.
- ^ Hegedüs, Ramón, Åkesson, Susanne; Wehner, Rüdiger and Horváth, Gábor. 2007. "Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies". Proc. R. Soc. A 463 (2080): 1081–1095. doi:10.1098/rspa.2007.1811. ISSN 0962-8452.
- ^ Ropars, G. et al., 2011. A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science. Available at: http://rspa.royalsocietypublishing.org/content/early/2011/10/28/rspa.2011.0369.abstract [Accessed December 5, 2011].
- ^ Pynchon,Thomas, 2007. Against the Day. Penguin. ISBN 0143112562 p. 114.
- ^ Ibid. pp. 119-428.
- ^ Pullman, Philip, 2007. The Amber Spyglass, Deluxe 10th Anniversary Edition. Knopf. ISBN 0375846735 p. 226.
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