Demystifying the Viking “sun stone”
Scientists believe a crystal found in an English wreck off the Channel Island of Alderney may indeed be the legendary “sun stone,” a mineral said to have helped the Vikings reach North America with neither map nor compass. The find boosts the theory that minerals, like Iceland spar, kept them on course by locating the sun on cloudy days or when it hovered below the horizon .
The crystal was found in the wreck of an English ship that sank in 1592. It “may support the use of the calcite crystal for navigation purposes,” researchers wrote in the Proceedings of the Royal Society, a scientific journal. Because the crystal’s creates a double refraction of light, the sun’s position can be pinpointed with great accuracy. By rotating the crystal against the eye until the darkness of the two shadows are equal, the sun’s position can pinpointed with remarkable accuracy, the researchers say.
The Alderney crystal was likely used to improve the ship’s compass readings. Sun stones are also mentioned in the inventories of several churches in 14th–15th century Iceland. The Vikings spoke of a magical gem that led them to American content hundreds of years before Columbus. One Norse saga describes how, on a cloudy day, King Olaf wanted to know where the sun was: “The King made them fetch the solar stone and held it up and saw where light radiated from the stone and thus directly verified Sigur’s prediction.”
Guy Ropars of the University of Rennes in the journal Proceedings of the Royal Society: “Alderney-like crystals could really have been used as an accurate optical sun compass as an aid to ancient navigation. It permits the observer to follow the azimuth of the sun, far below the horizon with an accuracy as great as plus or minus one degree. ”