One of the most interesting story was that of the 'sunstones', specially carved crystal blocks that were employed in navigation during overcast days. They were mentioned in the Saga of Saint Olaf.
A new finding has revealed that the legend might not have been so far from the truth. Although none of the purported crystals were found in viking ships, a similar stone found on a British shipwreck seems to prove that they were a reality.
The shipwreck was found near the Channel Islands where it sunk in Elizabethan times. The block was stored among other navigation tools in the shipwreck's hull.
A chemical analysis of the block revealed that it is of Scandinavian origin, specifically Icelandic Spar, or calcite.
In its present state it is hard to imagine how the crystal would have been useful to ancient mariners. Its surface has been dulled by sand and included with mineral intrusions after standing in seawater for so long.
Photo: Elderney Museum
But in its pristine state, centuries ago, the crystal would have been clear and able to refract any amount of sunlight. Because of their chemical composition, light refracting through it causes a double image to appear. But if you rotate the block in perfect alignment with an east-west axis, the images become one, and tells the mariners the ship's exact direction.
Because the crystal is highly refractive, they can capture light even in very overcast days or at twilight.
It was, in effect, a compass that could be used almost to the point of darkness.
source: daily Mail 3.8.13
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