[Bernard Marx]

The term "sunstone" is a bit confusing to those like me who work with minerals. It generally refers to a type of gem-quality labradorite or andesine feldspar found in Oregon, India and Tanzania mainly. Optical calcite is very different stuff. In the referenced article the name refers to any mineral used by the Vikings to locate the sun for navigation purposes.

It's long been believed that the mineral iolite (cordierite) was used for Viking navigation. A friend who comes from strong Nordic roots and is an accomplished gemologist/mineralogist put together this nice explanation on her website: Viking Sunstone

[decimon]

Thanks.

[ApplegateRanch]

Thanks. It’s been over 40 years since I took my introductory mineralogy classes; and never kept it up.

I always think of “sunstones” as those artificial glass teardrop things filled with bronze or copper fillings.