Magnetite As A Compass
Aside from sunstone or the so-called Icelandic spar, there was another object the Vikings were using when they were sailing. It was an object that could help them in the fog. When the Valkyrie had traded some good in China, they had bought a mineral called magnetite. With the use of magnetite, the Vikings created a compass. Using our world’s magnetic pull when they could pass the thickest fog that they could encounter. It means they could go anywhere they where they wanted to be.

Magnetite As A Compass