A little of topic, but it seems suitable for Skyrim.

New evidence has emerged of how the Vikings used Sunstones– translucent crystals of minerals such as calcite – to navigate using the sun long before the compass was invented in Europe. Here's the link

http://www.newscientist.com/article/dn20052-vikings-crystal-clear-method-of-navigation.html

Just a further example of how cool Vikings were. When I first read it in the paper it screamed Skyrim at me. Maybe this is how the magic compass works?

Or it would be a cool quest if a crystal you held could lead you to those hidden Dragon Walls, similar to the magic sword in Shadow of the Collosus.

Sorry. Didn't see duplicate topic http://www.gamesas.com/index.php?/topic/1163627-vikings-discovered-america-using-navigation-crystals/

Did a search for Sunstones though and couldn't find anything.