The sunstone ( is, sólarsteinn) is a type of

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ...

attested in several 13th–14th-century written sources in

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its ...

, one of which describes its use to locate the Sun in a completely overcast sky. Sunstones are also mentioned in the inventories of several churches and one

monastery A monastery is a building or complex of buildings comprising the domestic quarters and workplaces of monastics, monks or nuns, whether living in communities or alone ( hermits). A monastery generally includes a place reserved for prayer whic ...

in 14th–15th-century Iceland and

Germany Germany, officially the Federal Republic of Germany (FRG),, is a country in Central Europe. It is the most populous member state of the European Union. Germany lies between the Baltic and North Sea to the north and the Alps to the sou ...

. A theory exists that the sunstone had polarizing attributes and was used as a navigational instrument by seafarers in the

Viking Age The Viking Age () was the period during the Middle Ages when Norsemen known as Vikings undertook large-scale raiding, colonizing, conquest, and trading throughout Europe and reached North America. It followed the Migration Period The ...

. A stone found in 2002 off

Alderney Alderney (; french: Aurigny ; Auregnais: ) is the northernmost of the inhabited Channel Islands. It is part of the Bailiwick of Guernsey, a British Crown dependency. It is long and wide. The island's area is , making it the third-larges ...

, in the wreck of a 16th-century warship, may lend evidence of the existence of sunstones as navigational devices.

Sources

One

medieval In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...

source in Iceland, " Rauðúlfs þáttr", mentions the sunstone as a mineral by means of which the sun could be located in an overcast and snowy sky by holding it up and noting where it emitted, reflected or transmitted light (''hvar geislaði úr honum''). Sunstones are also mentioned in ' (13th century) and in church and monastic inventories (14th–15th century) without discussing their attributes. The sunstone texts of ''Hrafns saga Sveinbjarnarsonar'' were copied to all four versions of the medieval

hagiography A hagiography (; ) is a biography of a saint or an ecclesiastical leader, as well as, by extension, an adulatory and idealized biography of a founder, saint, monk, nun or icon in any of the world's religions. Early Christian hagiographies migh ...

'' Guðmundar saga góða''. The description in "Rauðúlfs þáttr" of the use of the sunstone is as follows:

Allegorical nature of the medieval texts

Two of the original medieval texts on the sunstone are

allegorical As a literary device or artistic form, an allegory is a narrative or visual representation in which a character, place, or event can be interpreted to represent a hidden meaning with moral or political significance. Authors have used allegory ...

. ''Hrafns saga Sveinbjarnarsonar'' contains a burst of purely allegorical material associated with Hrafn’s slaying. This involves a celestial vision with three highly cosmological

knight A knight is a person granted an honorary title of knighthood by a head of state (including the Pope) or representative for service to the monarch, the church or the country, especially in a military capacity. Knighthood finds origins in the G ...

s, recalling the horsemen of the

Apocalypse Apocalypse () is a literary genre in which a supernatural being reveals cosmic mysteries or the future to a human intermediary. The means of mediation include dreams, visions and heavenly journeys, and they typically feature symbolic imager ...

. It has been suggested that the horsemen of Hrafns saga contain allegorical allusions to the

winter solstice The winter solstice, also called the hibernal solstice, occurs when either of Earth's poles reaches its maximum tilt away from the Sun. This happens twice yearly, once in each hemisphere (Northern and Southern). For that hemisphere, the winte ...

and the

four elements Classical elements typically refer to earth, water, air, fire, and (later) aether which were proposed to explain the nature and complexity of all matter in terms of simpler substances. Ancient cultures in Greece, Tibet, and India had simil ...

as an omen of Hrafn’s death, where the sunstone also appears. "Rauðúlfs þáttr", a tale of Saint Olav, and the only medieval source mentioning how the sunstone was used, is a thoroughly allegorical work. A round and rotating house visited by Olav has been interpreted as a model of the

cosmos The cosmos (, ) is another name for the Universe. Using the word ''cosmos'' implies viewing the universe as a complex and orderly system or entity. The cosmos, and understandings of the reasons for its existence and significance, are studied in ...

and the human

soul In many religious and philosophical traditions, there is a belief that a soul is "the immaterial aspect or essence of a human being". Etymology The Modern English noun '':wikt:soul, soul'' is derived from Old English ''sāwol, sāwel''. The ea ...

, as well as a

prefiguration Prefiguration may refer to: * Prefiguration (politics), the reflection of a future society being sought by a group * Prefiguration (theology) Typology in Christian theology and biblical exegesis is a doctrine or theory concerning the relati ...

of the Church. The intention of the author was to achieve an

apotheosis Apotheosis (, ), also called divinization or deification (), is the glorification of a subject to divine levels and, commonly, the treatment of a human being, any other living thing, or an abstract idea in the likeness of a deity. The term h ...

of St. Olav, through placing him in the symbolic seat of

Christ Jesus, likely from he, יֵשׁוּעַ, translit=Yēšūaʿ, label= Hebrew/Aramaic ( AD 30 or 33), also referred to as Jesus Christ or Jesus of Nazareth (among other names and titles), was a first-century Jewish preacher and religi ...

. The house belongs to the

genre Genre () is any form or type of communication in any mode (written, spoken, digital, artistic, etc.) with socially-agreed-upon conventions developed over time. In popular usage, it normally describes a category of literature, music, or other ...

of "abodes of the sun," which seemed widespread in medieval literature. St. Olav used the sunstone to confirm the time reckoning skill of his host right after leaving this allegorical house. He held the sunstone up against the snowy and completely overcast sky and noted where light was emitted from it (the Icelandic words used do not make it clear whether the light was reflected by the stone, emitted by it or transmitted through it). It has been suggested that in "Rauðúlfs þáttr" the sunstone was used as a symbol of the

Virgin Virginity is the state of a person who has never engaged in sexual intercourse. The term ''virgin'' originally only referred to sexually inexperienced women, but has evolved to encompass a range of definitions, as found in traditional, modern ...

, following a widespread tradition in which the virgin birth of Christ is compared with glass letting a ray of the sun through. The allegories of the above-mentioned texts exploit the symbolic value of the sunstone, but the church and monastic inventories, however, show that something called sunstones did exist as physical objects in Iceland. The presence of the sunstone in "Rauðúlfs þáttr" may be entirely symbolic but its use is described in sufficient detail to show that the idea of using a stone to find the sun's position in overcast conditions was commonplace.

Possibility of sunstones for orientation and navigation

Danish archaeologist Thorkild Ramskou posited that the "sunstone" could have been one of the minerals (

cordierite Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate. Iron is almost always present and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: to . A high-tempera ...

or Iceland spar) that polarize light and by which the

azimuth An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematicall ...

of the sun can be determined in a partly overcast sky or when the sun is just below the horizon. The principle is used by many animals; and polar flights applied the idea before more advanced techniques became available. Ramskou further conjectured that Iceland spar could have aided

navigation Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...

in the open sea in the Viking period. This idea has become very popular, and research as to how a "sunstone" could be used in nautical navigation continues, often in the context of the Uunartoq disc. Research in 2011 by Ropars et al., confirms that one can identify the direction of the sun to within a few degrees in both cloudy and twilight conditions using Iceland spar and the naked eye. The process involves moving the stone across the visual field to reveal a yellow entoptic pattern on the

fovea Fovea () (Latin for "pit"; plural foveae ) is a term in anatomy. It refers to a pit or depression in a structure. Human anatomy * Fovea centralis of the retina * Fovea buccalis or Dimple * Fovea of the femoral head *Trochlear fovea of the f ...

of the eye. Alternatively, a dot can be placed on top of the crystal so that when you look at it from below, two dots appear, because the light is “depolarised” and fractured along different axes. The crystal can then be rotated until the two points have the same luminosity. The angle of the top face now gives the direction of the sun. Attempts to replicate this work in both Scotland and off the coast of Turkey by science journalist Matt Kaplan and mineralogists at the British Geological Survey in 2014 failed. Kaplan communicated with Ropars, and neither could understand why the samples of Iceland spar that were being used during the trials did not reveal the sun's direction, with the author hypothesizing that the stones require some experience to be handled effectively. The recovery of a piece of Iceland spar from an Elizabethan ship that sank near Alderney in 1592 suggests the possibility that this navigational technology may have persisted after the invention of the magnetic

compass A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with ...

. Although the stone was found near a navigational instrument, its use remains uncertain. Beyond nautical navigation, a polarizing crystal would have been useful as a

sundial A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a fl ...

, especially at high

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north po ...

s with extended hours of twilight, in mountainous areas, or in partly overcast conditions. This would have required the polarizing crystal to be used in conjunction with known landmarks. Churches and monasteries would have valued such an object as an aid to keep track of the canonical hours. A Hungarian team proposed that a sun compass artifact with crystals might also have allowed Vikings to guide their boats at night. A type of crystal they called sunstone can use scattered sunlight from below the horizon as a guide. What they suggest is that Iceland spar crystals were used in combination with

Haidinger's brush Haidinger's brush, more commonly known as Haidinger's brushes is an image produced by the eye, an entoptic phenomenon, first described by Austrian physicist Wilhelm Karl von Haidinger in 1844. Haidinger saw it when he looked through various mine ...

. If so, Vikings could have used them in the northern latitudes where it never becomes completely dark in summer. In areas of confused magnetic deviation (such as the

Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 ...

coast), a sunstone could have been a more reliable guide than a magnetic compass.

References

Turville-Petre, Joan E. (Trans.) (1947).
The story of Rauð and his sons
'. ''Payne Memorial Series II''. Viking Society for Northern Research. . Faulkes, Anthony. 1966. " Rauðúlfs þáttr: A study". '' Studia Islandica'' 25. Heimspekideild Háskóla Íslands og Bókaútgáfa Menningarsjóðs.

Reykjavík Reykjavík ( ; ) is the capital and largest city of Iceland. It is located in southwestern Iceland, on the southern shore of Faxaflói bay. Its latitude is 64°08' N, making it the world's northernmost capital of a sovereign state. With a pop ...

. . 92 pp. Sample, Ian
Crystals may have aided Viking sailors
. ''

Guardian Guardian usually refers to: * Legal guardian, a person with the authority and duty to care for the interests of another * ''The Guardian'', a British daily newspaper (The) Guardian(s) may also refer to: Places * Guardian, West Virginia, Unite ...

'' (Manchester, UK) p. 8. 7 February 2007. Retrieved December 27, 2010. "''Tests aboard a research vessel in the

Arctic ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, ...

found that certain crystals can be used to reveal the position of the sun, a trick that would have allowed early explorers to ascertain their position and navigate, even if the sky was obscured by cloud or fog.''" Helgadóttir, Guðrún P (ed.). 1987. ''Hrafns Saga Sveinbjarnarsonar''. Oxford:

Clarendon Press Oxford University Press (OUP) is the university press of the University of Oxford. It is the largest university press in the world, and its printing history dates back to the 1480s. Having been officially granted the legal right to print books ...

. . 267 pp. Karlsson, Stefán (ed.).1983. ''Guðmundar sögur biskups I: Ævi Guðmundar biskups, Guðmundar saga A''. ''Editiones Arnamagnæanæ, Series B'' (6). København:

C.A. Reitzels Forlag CA or ca may refer to: Businesses and organizations Companies * Air China (IATA airline code CA) * CA Technologies, a U.S. software company * Cayman Airways, a Cayman Islands airline * Channel America, a defunct U.S. television network * Classic ...

. . 262 pp. Vilhjalmsson, Thorsteinn. 1997.
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Disputatio ''Disputatio'' is an international journal of philosophy in the analytic tradition. It is currently owned by the Philosophy Centre of the University of Lisbon and managed by the LanCog research group. The journal is a non-profit publishing ventur ...

'', (II): 89–114. Johnsen, Oscar Albert and Jón Helgason (eds.). 1941. ''Saga Óláfs konungs hins helga. Den store saga om Olav den hellige. Efter pergamenthandskrift i Kungliga Biblioteket i Stockholm nr. 2 4to med varianter fra andre handskrifter''. ("Saga of King Olaf the Holy. The great saga of Olav the Holy. After the parchment manuscript no. 2 4to in the Royal Library in Stockholm with variants from other manuscripts.") Oslo: Norsk Historisk Kjeldeskrifts-Institutt, Vol. II. pp. 670–1 Einarsson, Árni. 2010. Sólarsteinninn: tæki eða tákn. (Summary in English: Sunstone: fact or fiction). '' Gripla'' 21 (1) 281–97 Árni Magnússon Institute. . Einarsson, Árni. 1997. "Saint Olaf’s dream house. A medieval cosmological allegory". ''

Skáldskaparmál ''Skáldskaparmál'' (Old Norse: 'The Language of Poetry'; c. 50,000 words; ; ) is the second part of the '' Prose Edda''. The section consists of a dialogue between Ægir, the divine personification of the sea, and Bragi, the god of poetry, ...

'' 4: 179–209, Reykjavík: Stafaholt. Einarsson, Árni. 2001. The symbolic imagery of

Hildegard of Bingen Hildegard of Bingen (german: Hildegard von Bingen; la, Hildegardis Bingensis; 17 September 1179), also known as Saint Hildegard and the Sibyl of the Rhine, was a German Benedictine abbess and polymath active as a writer, composer, philosopher ...

as a key to the allegorical Raudulfs thattr in Iceland. '' Erudiri Sapientia'', Studien zum Mittelalter und zu seiner Rezeptionsgeschichte (Studies on the Middle Ages and their reception history); II: 377–400. Loescher, G. 1981. "Rauðúlfs þáttr". ''Zeitschrift für deutsches Altertum und deutsche Literatur'' ('' ZfDA'') 110: 253-266. Breeze, Andrew. 1999.
The Blessed Virgin and the Sunbeam Through Glass
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External links

The Fabled Viking Sunstone
Icelandic culture History of navigation Navigational equipment Polarization (waves) Gemstones in culture sv:Islandsspat#Solsten

Sources

Allegorical nature of the medieval texts

Possibility of sunstones for orientation and navigation

See also

References

External links