Sunstone (medieval)

Two of the original medieval texts on the sunstone are allegorical. Hrafns saga Sveinbjarnarsonar contains a burst of purely allegorical material associated with Hrafn's slaying. This involves a celestial vision with three highly cosmological knights, recalling the horsemen of the Apocalypse. It has been suggested that the horsemen of Hrafns saga contain allegorical allusions to the winter solstice and the four elements 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 and the human soul, as well as a prefiguration of the Church. The intention of the author was to achieve an apotheosis of St. Olav, through placing him in the symbolic seat of Christ. The house belongs to the genre 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, 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 use for orientation and navigation==

Danish archaeologist Thorkild Ramskou posited that the "sunstone" could have been one of the minerals (cordierite or Iceland spar) that polarize light and by which the azimuth of the sun can be determined in a partly overcast sky or when the sun is just below the horizon. often in the context of the Uunartoq disc. Research in 2011 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. 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, especially at high latitudes 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. In areas of confused magnetic deviation (such as the Labrador coast), a sunstone could have been a more reliable guide than a magnetic compass. ==See also==