How the Vikings may have used calcite to locate the position of the Sun in a cloudy sky

It has been said that the legendary Vikings used a “Sun Stone” on cloudy days to navigate across the Atlantic Ocean to the eastern shores of America a thousand years ago.
What is this Sun Stone? Is it a magical artifact? How was it used?
Well, I looked online and I found that this transparent crystal called calcite has an interesting property called birefringence-as light enters into the crystal, it breaks up into two paths. But here’s the cool part: each beam is linearly polarized and they are perpendicularly oriented to one another.
And I found or something else pretty cool: 90° away from the location of the Sun in the sky, the sky is partially linearly polarized parallel to the horizon. So when the Sun is near the horizon, there is a great arc overhead where the sky has partially linearly polarized light. The video clip will demonstrate how to find this arc. Do this carefully, and the radiant of the arc will be the location of the Sun-even if the sky is completely covered with clouds!
My guess is that the Vikings made use of calcite to pinpoint the Sun’s location in the sky in a similar manner on their voyages to navigate across the stormy oceans. Calcite of this quality can be found in Iceland where some of them settled along the way.
There is no proof though that the legendary Sun Stone is actually calcite, but it is a nonetheless a pretty good guess!