Did Vikings navigate with 'sunstone'?

A Viking warship replica, Havhingsten af Glendalough (the Sea Stallion of Glendalough), makes its way into Dublin's port in 2007. New research suggests the Vikings used sunstones to navigate in cloudy and foggy conditions.

By John Roach
Vikings could have navigated the oceans in inclement weather with the aid of a crystal that pinpointed the sun's location behind banks of clouds and fog, a new study suggests. Such a tool, known as a sunstone, is known from legend, but until now experimental evidence that it could actually work as hypothesized was lacking. Article here