Iolite is also called Water Sapphire and is the name for the gem variety of Cordierite. It was thought to have been used by the Vikings to aid with navigation, by acting as a polarising filter to help them determine the position of the sun on cloudy days. It was first discovered in 1813 and named after Louis Cordier, the French Geologist. The more common name Iolite comes from the Greek for Violet.
Cordierite, Water Sapphire
7 - 7.5
Australia, Brazil, India, Madagascar, Sri Lanka, Burma