Iolite

Iolite (also known as the mineral cordierite), is a magnesium iron alumino-silicate. It is also called water sapphire because it looks very much like a blue sapphire, and was originally used for nautical purposes. When Leif Eriksson and the other legendary Viking explorers ventured far out into the Atlantic Ocean, away from any coastline that could help them determine position, they used thin pieces of iolite as the world's first polarizing filter. Looking through an iolite lens, they could determine the exact position of the sun, which allowed them to navigate safely.

The property that made iolite so valuable to the Vikings is extreme pleochroism. The stone is extremely pleochroic, which means it appears different colours depending upon which direction the stone is viewed. Iolite has three pleochroic directions. In one direction, it appears blue, in another bluish gray and in the other grayish yellow. It is being used extensively in jewellery today because it resembles tanzanite but is much less expensive because it is more plentiful.

Iolite was once thought to have the ability to increase one's faith. It is the talisman for people named Irene. Iolite is different colors in different directions in the crystal. A cube cut from iolite will look a violetish blue almost like sapphire from one side, clear as water from the other, and a honey yellow from the top