Iolite Gemstone. Known as the gemstone of the Vikings, Iolite is a blue-violet colored gemstone often mistaken for sapphire or tanzanite. Unknown to classical ancient Mediterranean cultures, it was used by Norse and Viking explorers to navigate. Mined from deposits in Norway and Greenland, this exceptional gemstone changes colors depending up the direction it is oriented - this allowing crude navigator even without a fix on the sun or stars. Called "water sapphire" by some as it is clear from one direction, its darkest blue shade is seen when held 90 degrees from the sun. The name iolite comes from the Greek ios, which means violet. In the 19th century it was known as "cordierite", after a French geologist, Pierre L. Cordier, who had "discovered" the gemstone for the benefit of Western Europe. Iolite is usually a very richly textured purplish blue when cut properly.