Viking Sunstone (e.g., Iceland Spar) Double Refraction, Not Direction of the Sun

Viking Sunstone (e.g., Iceland Spar) Double Refraction, Not Direction of the Sun. This demonstrates double refraction, not the direction of the sun. The sun stone can be used to find the direction of the sun on a cloudy day, but unfortunately this is not one of them. This method can’t be used for navigation.

[rynait]

have you figured out how they find the sun? in your video referencing geometric refraction against the lines seen through (onto paper), mean you did not find the sun at all.

[bvanpelt]

This crystal figures prominently in Thomas Pynchon's Against the Day.