Helgustaðanáma
Follow the coastal road past Mjóeyri, and continue southeast (around 4½ miles) to reach Helgustaðanáma, an old Iceland spar mine. These types of "spars" in Iceland are actually crystallized calcium carbonate, called "silfurberg" in Iceland. A short trail from an information board leads up to the opening. Iceland spar's unusual light-polarizing properties and the Nicol prisms made from it were crucial components for microscopes and instruments measuring optical activity, and the site was mined from the 16th until the 21st century. It's a popular belief that Iceland spar was used by Vikings as "sunstones" to help them navigate. Small pieces of Iceland spar lie around the entrance, but it is strictly forbidden to take it.
