Iceland spar

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Iceland spar, formerly called Iceland crystal (Icelandic: silfurberg [ˈsɪlvʏrˌpɛrk], lit.'silver-rock') and also called optical calcite, is a transparent variety of calcite, or crystallized calcium carbonate, originally brought from Iceland, and used in demonstrating the polarization of light.[1][2]

Formation and Composition[edit]

Calcite rhombohedral crystal structure

Iceland spar, or calcite, is a colourless, transparent variety of calcium carbonate (CaCO3).[3] It crystallizes in the trigonal system, typically forming rhombohedral crystals.[4] It has a Mohs hardness of 3 and exhibits double refraction, splitting a ray of light into two rays that travel at different speeds and directions.[3][5]

Iceland spar forms in sedimentary environments, mainly limestone and dolomite rocks, but it also forms in hydrothermal veins and evaporite deposits.[6] It precipitates from solutions rich in calcium and carbonate ions, influenced by temperature, pressure, and impurities.[6][7]

The most common crystal structure of Iceland spar is rhombohedral, but other structures, such as scalenohedral or prismatic, can form depending on formation conditions.[8][9] Iceland spar is primarily found in Iceland but can occur in different parts of the world with suitable geological conditions.[3][10]

Characteristics and Optical Properties[edit]

Calcite crystal birefringence

Iceland spar is characterized by its large, readily cleavable crystals, easily divided into parallelepipeds.[11][12] This feature makes it easily identifiable and workable. One of the most remarkable properties of Iceland spar is its birefringence, where the crystal's refractive index differs for light of different polarizations.[11][12] When a ray of unpolarized light passes through the crystal, it is divided into two rays of mutually perpendicular polarization directed at various angles. This double refraction causes objects seen through the crystal to appear doubled.

Iceland spar possesses several optical properties other than double refraction and birefringence. It is highly transparent to visible light, allowing light to pass through with minimal absorption or scattering, which is ideal for optical applications requiring clarity.[13] Iceland spar can produce vivid colours when viewed under polarized light due to its birefringent nature.[14] This effect is known as the "Becke line" and can be used to determine a mineral's refractive index.[15][16] Additionally, Iceland spar is optically active, meaning it can rotate the plane of polarization of light passing through it, a property resulting from its asymmetrical atomic arrangement.[17] These optical properties contribute to the mineral's scientific use and aesthetic appeal.

Historical Significance[edit]

Iceland spar holds historical importance in optics and the study of light.[18] One of its most notable properties is its ability to exhibit double refraction.[18] This phenomenon was first described by the Danish scientist Erasmus Bartholin in 1669, who observed it in a specimen of Iceland spar.[19]

The study of double refraction in Iceland spar played a role in developing the wave theory of light. Scientists such as Christiaan Huygens,[20] Isaac Newton, and Sir George Stokes studied this phenomenon and contributed to our understanding of light as a wave.[21][22] Huygens, in particular, used double refraction to support his wave theory of light, in contrast to Newton's corpuscular theory.[23][24] Augustin-Jean Fresnel published a complete explanation of double refraction in light polarization in the 1820s.[25]

The understanding of double refraction in Iceland spar also led to the development of polarized light microscopy, which is used in various scientific fields to study the properties of materials.[26][27] Iceland spar has been used historically in optical instruments like polarizing microscopes and navigation equipment.[26]

Mining[edit]

Mines producing Iceland spar include many mines producing related calcite and aragonite. Iceland spar occurs in various locations worldwide, historically named after Iceland due to its abundance on the island.[28] Other productive sources include China and the greater Sonoran Desert region, in Santa Eulalia, Chihuahua, Mexico, and New Mexico, United States.[29][30][31] The clearest specimens, as well as the largest, have been from the Helgustaðir mine in Iceland.[32]

Uses[edit]

Iceland spar, possibly the Icelandic medieval sun stone used to locate the sun in the sky when obstructed from view[33]

It has been speculated that the sunstone (Old Norse: sólarsteinn, a different mineral from the gem-quality sunstone) mentioned in medieval Icelandic texts such as Rauðúlfs þáttr was Iceland spar, and that Vikings used its light-polarizing property to tell the direction of the sun on cloudy days for navigational purposes.[33][34] The polarization of sunlight in the Arctic can be detected,[35] and the direction of the sun identified to within a few degrees in both cloudy and twilight conditions using the sunstone and the naked eye.[36] The process involves moving the stone across the visual field to reveal a yellow entoptic pattern on the fovea of the eye, probably Haidinger's brush. The recovery of an Iceland spar sunstone from a ship of the Elizabethan era that sank in 1592 off Alderney suggests that this navigational technology may have persisted after the invention of the magnetic compass.[37][38]

William Nicol (1770–1851) invented the first polarizing prism, using Iceland spar to create his Nicol prism.[39]

See also[edit]

Cultural impact[edit]

The Thomas Pynchon novel Against the Day uses the doubling effect of Iceland spar as a theme.[40]

References[edit]

  1. ^ Public Domain This article incorporates text from this source, which is in the public domainPorter, Noah, ed. (1913). "Polarimetry". Webster's Dictionary. Springfield, Massachusetts: C. & G. Merriam Co.
  2. ^ "Iceland spar". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  3. ^ a b c Kristjansson, Leo (2002). "Iceland Spar: The Helgustadir Calcite Locality and its Influence on the Development of Science". Journal of Geoscience Education. 50 (4): 419–427. Bibcode:2002JGeEd..50..419K. doi:10.5408/1089-9995-50.4.419. ISSN 1089-9995.
  4. ^ Hughes, H. Herbert., Iceland spar and optical fluorite: U. S. Bureau of Mines, Information Circular 6468 (1931)
  5. ^ Wada, Shinobu; Suzuki, Hitomi (2003-01-06). "Calcite and fluorite as catalyst for the Knövenagel condensation of malononitrile and methyl cyanoacetate under solvent-free conditions". Tetrahedron Letters. 44 (2): 399–401. doi:10.1016/S0040-4039(02)02431-0. ISSN 0040-4039.
  6. ^ a b Rollion-Bard, Claire; Marin-Carbonne, Johanna (2011-06-01). "Determination of SIMS matrix effects on oxygen isotopic compositions in carbonates". Journal of Analytical Atomic Spectrometry. 26 (6): 1285–1289. doi:10.1039/C0JA00213E. ISSN 1364-5544.
  7. ^ Morse, John W.; Arvidson, Rolf S.; Lüttge, Andreas (2007-02-01). "Calcium Carbonate Formation and Dissolution". Chemical Reviews. 107 (2): 342–381. doi:10.1021/cr050358j. ISSN 0009-2665. PMID 17261071.
  8. ^ Skomorovsky, Valery; Kushtal, Galina; Tokareva (Lopteva), Lyubov (2022-03-25). "Iceland spar and birefringent filter (BF) development". Solar-Terrestrial Physics. 8 (1): 69–84. Bibcode:2022STP.....8a..69S. doi:10.12737/stp-81202209. ISSN 2500-0535.
  9. ^ Skropyshev, A. V. (1959). "Gaseous-Liquid Inclusions in Crystals of Iceland Spar". International Geology Review. 1 (9): 1–11. Bibcode:1959IGRv....1R...1S. doi:10.1080/00206815909473436. ISSN 0020-6814.
  10. ^ Cook, Robert B. (2009). "Mineral Oddities: Theme of the 2009 Tucson Gem & Mineral Show". Rocks & Minerals. 84 (1): 16–25. Bibcode:2009RoMin..84...16C. doi:10.3200/RMIN.84.1.16-25. ISSN 0035-7529.
  11. ^ a b Public Domain This article incorporates text from this source, which is in the public domainWebster, Noah (1828). "Birefringence". Webster's Dictionary. Springfield, Massachusetts: C. & G. Merriam Co.
  12. ^ a b Miers, Henry A., Mineralogy: an introduction to the scientific study of minerals. Nabu Press. ISBN 1-177-85127-X Chap. 6, p. 128.
  13. ^ Hughes, H. Herbert., Iceland spar and optical fluorite: U. S. Bureau of Mines, Information Circular 6468 (1931)
  14. ^ Skomorovsky, Valery; Kushtal, Galina; Tokareva (Lopteva), Lyubov (2022-03-25). "Iceland spar and birefringent filter (BF) development". Solar-Terrestrial Physics. 8 (1): 69–84. Bibcode:2022STP.....8a..69S. doi:10.12737/stp-81202209. ISSN 2500-0535.
  15. ^ Kristjansson, Leo (2002). "Iceland Spar: The Helgustadir Calcite Locality and its Influence on the Development of Science". Journal of Geoscience Education. 50 (4): 419–427. Bibcode:2002JGeEd..50..419K. doi:10.5408/1089-9995-50.4.419. ISSN 1089-9995.
  16. ^ Choi, Ju H.; Eichele, Chad; Lin, Yuan C.; Shi, Frank G.; Carlson, Bob; Sciamanna, Steven (2008-03-01). "Determination of effective refractive index of molecular diamondoids by Becke line method". Scripta Materialia. Viewpoint set no. 43 “Friction stir processing”. 58 (5): 413–416. doi:10.1016/j.scriptamat.2007.10.036. ISSN 1359-6462.
  17. ^ Kristjánsson, L. (2012-05-16). "Iceland spar and its legacy in science". History of Geo- and Space Sciences. 3 (1): 117–126. Bibcode:2012HGSS....3..117K. doi:10.5194/hgss-3-117-2012. ISSN 2190-5029.
  18. ^ a b Kristjansson, Leo (2002). "Iceland Spar: The Helgustadir Calcite Locality and its Influence on the Development of Science". Journal of Geoscience Education. 50 (4): 419–427. Bibcode:2002JGeEd..50..419K. doi:10.5408/1089-9995-50.4.419. ISSN 1089-9995.
  19. ^ Bartholin, Rasmus; Archibald, Thomas; Buchwald, Jed Z.; Møller Pedersen, Kurt (1991). Experiments on Birefringent icelandic crystal: with a facsimile of the original publication 1669. Acta historica scientiarum naturalium et medicinalium (Reprod. en fac-sim. ed.). Copenhagen: the Danish national library of science and medicine. ISBN 978-87-7709-010-3.
  20. ^ C. Huygens, Treatise on Light (Leiden: Van der Aa, 1690), translated by Silvanus P. Thompson, London: Macmillan, 1912, archive.org/details/treatiseonlight031310mbp; Project Gutenberg edition, 2005, gutenberg.org/ebooks/14725; Errata, 2016.
  21. ^ Public Domain This article incorporates text from a publication now in the public domainChambers, Ephraim, ed. (1728). "Isaac Newton". Cyclopædia, or an Universal Dictionary of Arts and Sciences (1st ed.). James and John Knapton, et al.
  22. ^ 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 1-177-14275-9 p. 269.
  23. ^ Huygens, Christiaan (1912). Treatise On Light. Osmania University, Digital Library Of India. Macmillan And Company., Limited.
  24. ^ Buenker, Robert J. (2022-05-15). "Newton's Theory of Light and Wave-Particle Duality" (PDF). East African Scholars Journal of Engineering and Computer Sciences. 5 (2): 21–31. doi:10.36349/easjecs.2022.v05i02.001.
  25. ^ Whittaker, E. T., A History of the Theories of Aether and Electricity. Dublin University Press, 1910.
  26. ^ a b Kristjansson, Leo (2002). "Iceland Spar: The Helgustadir Calcite Locality and its Influence on the Development of Science". Journal of Geoscience Education. 50 (4): 419–427. Bibcode:2002JGeEd..50..419K. doi:10.5408/1089-9995-50.4.419. ISSN 1089-9995.
  27. ^ Skomorovsky, Valery; Kushtal, Galina; Tokareva (Lopteva), Lyubov (2022-03-25). "Iceland spar and birefringent filter (BF) development". Solar-Terrestrial Physics. 8 (1): 69–84. Bibcode:2022STP.....8a..69S. doi:10.12737/stp-81202209. ISSN 2500-0535.
  28. ^ Russell, Daniel E . 17 February 2008. Retrieved December 31, 2010. "Helgustadir Iceland Spar Mine" mindat.org
  29. ^ 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"
  30. ^ Kelley, Vincent C. 1940. Retrieved December 31, 2010. "Iceland Spar in New Mexico". American Mineralogist, Volume 25, pp. 357-367
  31. ^ 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 CNKI:SUN:KJQB.0.2009-33-061
  32. ^ "Helgustaðanáma". Umhverfisstofnun (in Icelandic). Retrieved 2020-08-20.
  33. ^ a b The Viking Sunstone, from Polarization.net. Retrieved February 8, 2007.
  34. ^ Karlsen, Leif K. 2003. Secrets of the Viking Navigators. One Earth Press. ISBN 978-0-9721515-0-4, 220 pp.
  35. ^ 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.
  36. ^ 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].
  37. ^ "First Evidence of Viking-Like 'Sunstone' Found - Seeker". 2017-07-02. Archived from the original on 2017-07-02. Retrieved 2023-05-24.
  38. ^ Le Floch, A., Ropars, G., Lucas, J., Wright, S., Davenport, T., Corfield, M., & Harrisson, M. (2013). The sixteenth century Alderney crystal: a calcite as an efficient reference optical compass?. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 469(2153), 20120651.
  39. ^ Greenslade, Thomas B. Jr. "Nicol Prism". Kenyon College. Retrieved 23 January 2014.
  40. ^ "Pynchon's First Novel in 10 Years Has Sex, Explosives (Update1)". Bloomberg News. 2007-09-30. Archived from the original on 2007-09-30. Retrieved 2023-05-25.