Iolite: Gem of the Vikings

Viking explorers were the first to use thin pieces of iolite as a polarizing filter that allowed them to determine the exact position of the sun and thereby navigate safely between their homeland and the New World. The property that made this possible was the extreme pleochroism (the property of certain crystals of exhibiting different colors when viewed from different directions under transmitted light) of iolite. This gem has a variety of colors visible in different directions in the crystal. A cube cut from iolite will look blue/sapphire from one side, crystal clear from the other, and a honey yellow from on top.
The same property (pleochroism) that makes iolite useful as a tool for navigation creates problems for the cutter. Iolite must be cut from exactly the right direction or its colors will not be as brilliant.
The name iolite comes from the Greek ‘ion’, which means violet. It is a purplish blue when cut properly and it has a softness that makes it very pleasing to the eye and increasingly popular for use in jewelry. The deeper the blue the more valuable the gemstone, but overall, iolite is quite affordable. The Vikings probably got their iolite from deposits in Norway and Greenland, however, today It is mined in India, Sri Lanka, Mozambique, Zimbabwe, and Brazil.