In Norse legends, sunstones are said to have guided Viking seafarers to North America.
A report in the Proceedings of the Royal Society A says a form of rock known as Icelandic spar could have been the mythical sunstones because of its ability to polarize light, the BBC reported Wednesday.
Voyaging Vikings could have held them aloft and used that quality to determine the direction of the sun even when it was hidden by cloud cover, researchers said.
Icelandic spars, formed from crystallized calcium carbonate, are good polarizers and may have been the source material for the Vikings' sunstones, the study said.
Icelandic spars can be easily cleaved and crafted into a rhombus shape required for the polarizing effect, and one example has been discovered on the wreck of an Elizabethan ship that sank in 1592, the researchers said.
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