My ancestors, the Vikings,

were the first to reach modern America, WAY before Columbus, partially because of the 'sun stone', or Icelandic spar, mentioned in writings by St Olaf, from the 13th century, (and featured in the new History Channel series, 'Vikings'), allowed them to keep their bearings in the open ocean.

Because of the rhombohedral shape of calcite crystals, "they refract or polarize light in such a way to create a double image," Mike Harrison, coordinator of the Alderney Maritime Trust, told LiveScience. This means that if you were to look at someone's face through a clear chunk of Icelandic spar, you would see two faces. But if the crystal is held in just the right position, the double image becomes a single image and you know the crystal is pointing east-west, Harrison said, because they were created that way in nature, with such an alignment.