Researchers based at the University of Rennes in Brittany believe that a cloudy crystal discovered in the wreck of an Elizabethan ship sunk off the Channel Islands could be the substance described by the Norsemen as helping to locate the sun when obscured by cloud, the Independent reported.
Scientists have been trying to find evidence of the so-called sunstone after it was described in one Icelandic saga as a magical gem which, when held up to sky, would reveal the position of the sun even before dawn or after sunset.
Such a navigational aid could have helped the Vikings to gain the reputation as remarkable seafarers. Many historians even believe that they may have beaten Christopher Columbus as the first European visitors to America by hundreds of years.
University of Rennes scientists who studied the cigarette packet-shaped crystal discovered on board the wreck off Alderney suggest that Tudor sailors may have used the stone to navigate in much the same way as their Viking predecessors.
The stone, a calcite substance known as Iceland spar, was found by divers next to a pair of dividers, leading investigators to wonder whether it formed part of the navigational arsenal of the English vessel, which sank in 1592, some four years after the Spanish Armada.
There is no reference to such stones being used by Elizabethan seamen but the Icelandic sagas describe how the Viking king, Olaf, during snowy weather, asked a vassal, Sigur, to point to where the sun would be. To check the answer, "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".
Despite the literary references, no intact sunstone has been found on Viking sites.
"Alderney-like crystals could really have been used as an accurate optical sun compass as an aid to ancient navigation," Dr Guy Ropars wrote in the journal Proceedings of the Royal Society.
"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. The evolution of the Alderney crystal lends hope for identifying other calcite crystals in Viking shipwrecks, burials or settlements," he added.
The researchers also indicated that the failure so far to find intact sunstones in Viking burial sites might be due to the practice of cremating warriors, which would have caused the delicate crystals to shatter.